Peronia verruculata (Cuvier, 1830)

Dayrat, Benoit, Goulding, Tricia C., Apte, Deepak, Aslam, Sadar, Bourke, Adam, Comendador, Joseph, Khalil, Munawar, Ngo, Xuan Qu ảng, Tan, Siong Kiat & Tan, Shau Hwai, 2020, Systematic revision of the genus Peronia Fleming, 1822 (Gastropoda, Euthyneura, Pulmonata, Onchidiidae), ZooKeys 972, pp. 1-224 : 1

Peronia verruculata (Cuvier, 1830) Figs 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 106 , 107 , 108 , 109

Onchidium verruculatum Cuvier, 1830: 281; Semper 1880: 255-257, pl. 22, figs 3, 4; 1882: pl. 21, fig. 1 [only in part]; Bergh 1884a: 148-151, pl. VII, figs 7-12, pl. VIII, fig. 14; Farran 1905: 358-359, pl. VI, figs 13-22; Odhner 1919: 23; Hoffmann 1928: 44, 72-75 [only in part].

Peronia verruculata (Cuvier, 1830): Keferstein 1865a: pl. CIV, figs 9-12; Britton 1984: 183-184, fig. 2 [only in part]; Sun et al. 2014: 63; Liu et al. 2015: 753-754; Chang et al. 2018: 149-165, figs 1-8; Xu et al. 2018: 3.

Onchidium ferrugineum Lesson, 1831a: 128-130; Lesson 1831b: 300-302; Lesson 1832: 36-37, fig. 32.

Peronia ferruginea (Lesson, 1831a): Lesson 1833: 3 pp. with no pagination, pl. 19, figs 1, 2; Oken 1834b: 269-270; Gray 1850: 117; Adams and Adams 1855: 235; Tapparone Canefri 1883: 214.

Peronia savignii Récluz, 1869: 61. Syn. nov.

Peronia mauritiana : Mörch 1872a: 28; 1872b: 325 [non Peronia mauritiana Blainville, 1824].

Onchidium branchiferum Plate, 1893: 141, 183-185, pl. 11, figs 63, 64; Hoffmann 1928: 68, 75. Syn. nov.

Peronia branchifera (Plate, 1893): Labbé 1934a: 194.

Onchidium elberti Simroth, 1920: 297-298, pl. XX, figs 51-54.

Onchidium astridae Labbé, 1934b: 77-78, figs 18, 38, pl. I, fig. 5. Syn. nov.

Scaphis astridae ( Labbé, 1934b): Labbé 1934a: 213, fig. 46.

Peronia gaimardi Labbé, 1934a: 194-195, fig. 8. Syn. nov.

Peronia anomala Labbé, 1934a: 195-196. Syn. nov.

Paraperonia gondwanae Labbé, 1934a: 199-200, figs 19-22 [only in part]. Syn. nov.

Scaphis viridis Labbé, 1934a: 207-208, figs 31-34. Syn. nov.

Scaphis carbonaria Labbé, 1934a: 208-209, figs 35, 36. Syn. nov.

Scaphis gravieri Labbé, 1934a: 209-211, figs 37-40. Syn. nov.

Scaphis tonkinensis Labbé, 1934a: 211-212, figs 41-43. Syn. nov.

Scaphis lata Labbé, 1934a: 212, figs 44-45. Syn. nov.

Onchidium durum Labbé, 1934a: 220-221, figs 55-57. Syn. nov.

Peronia sp. ("group V"): Tagaki et al. 2019: 34.

Peronia persiae Maniei et al. 2020a: 507-514, figs 2-10. Syn. nov.

Type material.

Lectotype ( O. verruculatum ). Red Sea • lectotype, hereby designated, 30/26 mm; [locality not specified in the original description but most likely from the Red Sea]; MNHN-IM-2000-22941. One paralectotype was not found at the MNHN. Cuvier (1830: 46) did not accompany the name Onchidium verruculatum with a description but referred to a series of eight drawings by Savigny (1817: pl. 2, figs 3.1-3.8) in the famous Description de l’Egypte ("Descr. de l’Eg., moll. gaster., pl. II, f. 3"). For a collation of the Description de l’Egypte, including the text by Audouin (1826), see Baring (1838) and Sherborn (1897). Cuvier’s reference to Savigny’s illustrations is an indication ( ICZN 1999: Article 12.2). Onchidium verruculatum is available and the type series consists of the specimens illustrated by Savigny ( ICZN 1999: Article 72.4). Savigny illustrated two individuals which could belong to two distinct species given that there are (at least) two Peronia species in the Red Sea. One specimen (figs 3.1, 3.2) is much smaller than the other (fig. 3.3). One of the two individuals illustrated by Savigny is preserved at the MNHN in a jar with a label reading: "Savigny Description Egypte, Mer Rouge [Red Sea], syntype, pl. 2, fig. 3" (MNHN-IM-2000-22941). The specimen preserved at the MNHN looks like the individual illustrated on Savigny’s figures 3.1, 3.2. The ventral surface (fig. 3.2) looks exactly like the MNHN specimen (without the male parts outside, which were subsequently removed). The figure 3.3 illustrates a much larger individual which could not be located. No information was provided on sizes, except that the illustrations were of "natural length" (figures 3.1, 3.2) and "likely of natural length" (figure 3.3) according to Audouin (1826: 19). Given that it is unclear whether Savigny (unknowingly) illustrated one or two species, it is appropriate to designate the specimen preserved at the MNHN as the lectotype (MNHN-IM-2000-22941). The animals illustrated by Savigny (1817) were not accompanied by any species name, but they were named and described ten years later by Audouin (1826: 18-20) who referred to the figures 3.1-3.8 on Savigny’s plate 2 as Onchidium peronii . Interestingly, Audouin (1826: 19, our translation) wrote that this identification was suggested to him by Cuvier himself: "Mr. Cuvier, to whom we communicated Mr. Savigny’s drawing, believed he recognized Péron’s onchidie." Cuvier likely changed his mind and later decided that, for some reason, the specimens illustrated by Savigny were a distinct species he called Onchidium verruculatum . The lectotype is still well preserved, considering how old it is. The radula and the posterior (female) reproductive parts are still inside but only the deferens duct remains for the male copulatory parts. Its intestinal loops are of type I (Fig. 86A ). The number of papillae with eyes can hardly be counted on the dorsal notum of the lectotype because it has faded (only four papillae with eyes were counted).

Lectotype and paralectotypes ( Onchidium ferrugineum ). Indonesia • lectotype, 35/25 mm; havre de Doréry [spelling mistake for Dorey], à la Nouvelle-Guinée [now Manokwari harbor, West Papua]; MNHN-IM-2000-22951. • 2 paralectotypes, 33/20 and 26/18 mm; same collection data as for the lectotype; MNHN-IM-2000-22951. The lectotype was designated by Goulding et al. (2018: 75) to clarify the application of Onchidium ferrugineum . The two paralectotypes belong to Wallaconchis ater (Lesson, 1831a) because they lack dorsal gills, lack an accessory penial gland, and are characterized by a highly coiled penis. Labbé re-examined four specimens from the original type series but there are only three specimens left in the jar, so one specimen was lost by or after Labbé. The lectotype is well preserved. Its dorsal notum bears obvious gills. Its male opening is located below and to the left of the right ocular tentacle. Pieces of the deferent duct and of the flagellum of the accessory penial gland remain, but the muscular sac and the spine of the accessory gland are missing. The posterior (female) part of the reproductive system is still in place inside the lectotype. Its radula is missing. Its intestinal loops of type I (with a transitional loop at 4 o’clock) are illustrated here (Fig. 80A ).

Lectotype ( Peronia savignii ). Red Sea • lectotype, hereby designated, 30/26 mm; MNHN-IM-2000-22941. Récluz (1869: 61) created the species name Peronia savignii with a reference to Savigny’s (1817) illustrations as indication ("Descr. de l’Egypte, pl. II, f. 1-5"). There are only three figures on Savigny’s (1817) plate 2. Obviously, Récluz did not mean to refer to Tritonia (figs 1.1-1.12) or Bursatella (figs 2.1-2.13) but only to Peronia (figs 3.1-3.8). There is no easy explanation for the exclusion of figures 3.6-3.8 except that Audouin’s (1826) captions for Savigny’s (1817) figures 3.1-3.5 are on page 19 and those for figures 3.6-3.8 are on page 20. At any rate, Peronia savignii is available and the type series consists of the individuals illustrated by Savigny. The lectotype of Onchidium verruculatum (MNHN-IM-2000-22941) is logically part of the type series of P. savignii (in fact, a label already indicates that it is a syntype of P. savignii ). In order to clarify the application of P. savignii , the lectotype of O. verruculatum is also designated as the lectotype of P. savignii , and P. savignii remains what it has always been, a junior objective synonym of O. verruculatum .

Syntypes ( Onchidium branchiferum ). Philippines • 2 syntypes, 27/18 and 24/15 mm; Cavite, Manila [Luzon]; ZMB/Moll 11614. Both syntypes were completely dissected prior to the present study, likely by Plate himself, and all internal organs are either missing or destroyed. The type of intestinal loops could not be verified. Dorsal gills are present on the notum. The type series also includes six histological slides.

Holotype ( Onchidium elberti ). Indonesia • holotype, by monotypy, 24/20 mm; Südost-Celebes, Moena, Raha [now Raha, Muna Island, Sulawesi]; SMF 45248. The holotype was never dissected prior to the present study. The animal is more or less hemispherical. It was carefully opened dorsally to check and illustrate its intestinal loops of type I (Fig. 80B ). Dorsal gills are present on the notum.

Holotype ( Onchidium astridae ). Indonesia • holotype, by monotypy, 20/18 mm; Sorong door, Nouvelle-Guinée [Sorong, West Papua]; RBINS I.G.9223/MT.3822. The holotype, clearly labeled as " Oncidium Astridae Labbé,” was dissected by Labbé for the original description but is relatively well preserved. The radula, the posterior (female) reproductive parts, and the intestinal loops of type I (Fig. 80C ) are still in place inside the specimen. Male parts are missing. Dorsal gills are present on the notum (partly cut by Labbé). Note that the locality on the label of the holotype is indicated as Sorong, but with a question mark.

Lectotype and paralectotypes ( Peronia gaimardi ). Solomon Islands • lectotype, hereby designated, 44/27 mm; Vanikoro; 1829; JRC Quoy & JP Gaimard leg.; MNHN-IM-2000-33705. • 1 paralectotype, 35/30 mm; same collection data as for the lectotype; MNHN-IM-2000-33705. The type material also includes a paralectotype from Djibouti which could not be located with certainty (see below). Originally, no jar clearly labeled as the type material of Peronia gaimardi was found at the MNHN. The original description of P. gaimardi is based on three individuals, two individuals identified as Onchidium , from "Vanikoro (Quoy and Gaimard 1829)," and one individual identified as " Oncidium Peronii ," from "Obock, Récif de Clochettins (Gravier 1904)."

The two specimens from Vanikoro were found at the MNHN in a jar with three labels. One old label says " Onchidium [subsequently replaced by Peronia ] de Vanikoro, mm Quoy et Gaimard 1829." Another label only says “44” for unknown reasons. And a more recent label says " Peronia Vanikoro, M. Quoy et Gaimard 1829." There is no indication that those two specimens are part of the type series of P. gaimardi . However, there is only one jar of specimens collected by "Quoy et Gaimard 1829" from Vanikoro at the MNHN and, given that the size of the largest specimen (42/22 mm) provided by Labbé matches the size of the lectotype designated here, there is little doubt that those two individuals from Vanikoro were originally used by Labbé to describe P. gaimardi . The lectotype was dissected by Labbé. Its radula and male apparatus are missing. The female parts are still inside the animal. Its intestinal loops of type I are illustrated here (Fig. 80E ). Dorsal gills are present on the notum. The paralectotype from Vanikoro was not dissected by Labbé.

As for the paralectotype from Obock, Djibouti, it could not be traced with certainty, which does not matter given that it has no name-bearing function. Based on the original description ( Labbé 1934a: 194), the paralectotype from Djibouti was collected by Gravier in 1904 at the “Récif de Clochettins, Obock," that it measured 80/57 mm, and that its body was "very flattened." There is a jar at the MNHN with a label saying " Oncidium Peronii , Cuv. Obock M. Gravier 1904 - A Labbé, dét [for “déterminé,” i.e., identified] 1933." Another label says “F” for unknown reasons. All the information on the label matches the information provided by Labbé in the original description of P. gaimardi , and the size (80/60 mm) of the specimen perfectly matches the size of the paralectotype of P. gaimardi . That specimen is just an empty notum with dorsal gills (all internal organs are missing). However, for two reasons, it is extremely unclear whether that specimen is the paralectotype of P. gaimardi from Obock. First, there is yet a third label (which was covered by the "Obock, Gravier, 1904" label) saying that the specimen was, instead, collected by Jousseaume from the Red Sea ("Mer Rouge"). And, second, Labbé (1934a: 192) listed a specimen from the same locality ( “Récif de Clochettein [for Clochettins] (Obock)"), also collected by "Gravier 1904" and also identified as " Onchidium peronii " in his re-description of Peronia tongana . Therefore, given that there is only one jar at the MNHN with a specimen collected by Gravier in 1904 from Obock (there are other specimens from Obock at the MNHN, but not collected in 1904 by Gravier), and that the specimen may not even have been collected by Gravier, it is not possible to know whether that specimen is the paralectotype of P. gaimardi , a non-type material used by Labbé for a re-description of Peronia tongana , or even something completely different.

Lectotype and paralectotype ( Peronia anomala ). Red Sea • lectotype, hereby designated, 10/8 mm; 1893; Jousseaume leg.; MNHN-IM-2000-33678. • 1 paralectotype, 6/3 mm; same collection data as for the lectotype; MNHN-IM-2000-33678. Originally, no jar clearly labeled as the type material of Peronia anomala was found at the MNHN, but it could be traced back. The original description of P. anomala is based on two individuals (10/9 and 5/5 mm) from the Red Sea ("Mer Rouge") collected by Jousseaume in 1893. Several old jars were found at the MNHN with material collected from the Red Sea by Jousseaume. Most jars are labeled as “1892” for collecting date, one jar is labeled as “1893” (MNHN-IM-2000-33678), and another as “1823” (MNHN-IM-2000-33698). The jar with the (erroneous) collecting date of 1823 is the type series of Onchidium durum (see below). The jar with a collecting date of 1893 matches perfectly the information provided in Labbé’s original description of P. anomala and even the animal sizes match (MNHN-IM-2000-33678): these two specimens are considered to be the type series of P. anomala , and the largest specimen is designated as the lectotype. Both the lectotype and the paralectotype were dissected by Labbé. The radula and female and male reproductive parts of the lectotype are missing (the lack of penis and accessory penial gland, mentioned by Labbé, but likely due to the lectotype being not fully mature, cannot be checked). Dorsal gills are present on the notum. Its intestinal loops are not of type II ( Labbé 1934a: 195), but of type I instead (Fig. 86B ). The paralectotype is largely destroyed but bears dorsal gills on the notum.

Lectotype and paralectotypes ( Paraperonia gondwanae ). India • lectotype, hereby designated, 29/25 mm; Bombay [Mumbai]; MNHN-IM-2000-33681. • 1 paralectotype, 26/25 mm; same collection data as for the lectotype; MNHN-IM-2000-33681. • 1 paralectotype, 50/35 mm; same collection data as for the lectotype; MNHN-IM-2000-33682. Red Sea • 4 paralectotypes, 40/30 mm; 1892; Jousseaume leg.; MNHN-IM-2000-33683. • 13 paralectotypes, 32/25 to 25/20 mm; Red Sea; 1892; Jousseaume leg.; MNHN-IM-2000-33688. • 15 paralectotypes, 40/30 to 22/20 mm; Suez [Egypt, Red Sea]; 1878; Letourneux leg.; MNHN-IM-2000-33684. The type material mentioned in the original description also includes a paralectotype from Mauritius which could not be located with certainty at the MNHN, a paralectotype from the Red Sea which could not be located at the MNHN, and another individual missing from one of the jars from the Red Sea (see below). Most importantly, the type specimens belong to more than one species, so a lectotype is designated to clarify the application of the name P. gondwanae .

Originally, no jar clearly labeled as the type material of P. gondwanae was found at the MNHN, but most of the type material could be traced back. The original description of P. gondwanae is based on 38 individuals which Labbé, as often, listed in his article using italicized letters: a) three individuals from Bombay and one individual from the Red Sea ("mer Rouge"), for which Labbé gives the sizes 29/23 and 50/30 mm; b) one individual (60/50 mm) from Mauritius ( “île de France") collected by Mathieu; c) five individuals (40/27 mm) from the Red Sea ("mer Rouge") collected by Jousseaume in 1892; d) 15 individuals from Suez (Red Sea) collected by Letourneur in 1878; and e) 13 individuals from the Red Sea ("mer Rouge") collected by Jousseaume in 1892, for which Labbé gives the size 32/25 mm (for both d and e).

The specific name " gondwanae " was written in pencil only on two old jars at the MNHN. One jar contains four of the five " c " individuals collected from the Red Sea by Jousseaume in 1892 (MNHN-IM-2000-33683); the name " gondwanae " is written on the small label with the number “59;” the size of the four specimens (40/30 mm) matches the size provided by Labbé. Another jar contains the 13 " e " individuals collected from the Red Sea by Jousseaume in 1892 (MNHN-IM-2000-33688); this jar was found only labeled as "57 gondwanae ," i.e., with no locality, collector name, or collecting year, but the number of individuals and their size (32/25 to 25/20 mm) matches the size provided by Labbé (35/25 mm).

No other jar labeled as P. gondwanae was found at the MNHN, but most of the remaining type material could be traced back thanks to the matching of collector’s name, collecting date, specimen sizes, and the number of old jars from any given locality at the MNHN. There are only three old jars with specimens from Bombay at the MNHN. One jar contains seven Platevindex individuals collected by Roux in 1826. The two other jars contain the three " a " individuals from Bombay: one jar contains two individuals (29/25 and 26/25 mm) (MNHN-IM-2000-33681) and the other jar contains one individual (50/35 mm) (MNHN-IM-2000-33682), which sufficiently matches the sizes in Labbé’s original description (50/30 and 29/23 mm). There is only one old jar at the MNHN with 15 specimens (from 40/30 to 22/20 mm) from Suez collected by Letourneux ( “Letourneur” in the original description) in 1878 (there is another old jar of Peronia from Suez but collected by Jousseaume in 1889). That jar contains the " d " individuals of P. gondwanae from Suez (MNHN-IM-2000-33684). The " b " individual from Mauritius could not be traced with certainty at the MNHN. Indeed, there are two jars, each with a single specimen from Mauritius collected by Mathieu and identified as Oncidium Peronii by Labbé in 1933: one 65/40 specimen (MNHN-IM-2000-33687), and one 60/40 specimen (MNHN-IM-2000-33686). Both specimens match the size provided by Labbé for the " b " individual (60/50 mm). Labbé (1934a) listed only once a specimen from Mauritius by Mathieu in his entire work, and that specimen could be the one in either jar (i.e., MNHN-IM-2000-33686 or MNHN-IM-2000-33687). Finally, the " a " individual identified from the Red Sea could not be located.

The 29 mm long " a " individual from Bombay, dissected by Labbé, is designated here as the lectotype of Paraperonia gondwanae (MNHN-IM-2000-33681). Its radula and male parts are missing. Its intestinal loops are clearly of type I (Fig. 84A ) even though Labbé described loops of type V. The 50 mm long " a " individual from Bombay was also dissected by Labbé (MNHN-IM-2000-33682). Its radula and male parts are missing but its intestinal loops are of type V (Fig. 21B ), as in the original description, so it does not belong to P. verruculata but P. madagascariensis instead. Labbé dissected only two of the 15 specimens from Suez (MNHN-IM-2000-33684): the radula and the male parts are missing from both specimens (38/32 and 35/28 mm) but their intestinal loops are both of type I (Fig. 86D ), suggesting that they belong to P. verruculata , even though Labbé described loops of type V. Labbé dissected only one (40/30 mm) of the four specimens from Suez (MNHN-IM-2000-33683), acknowledging that maybe one specimen was lost: the radula and the male parts are missing, but its intestinal loops are of type V (Fig. 21C ), as in the original description, suggesting that it belongs to P. madagascariensis . Labbé dissected seven of the 13 specimens (assumed to be) from the Red Sea (MNHN-IM-2000-33688). Those specimens are all completely destroyed and extremely poorly preserved. An undissected individual (35/25 mm) from the same lot was dissected for the present study and its intestinal loops are of type I, suggesting that it belongs to P. verruculata (Fig. 86E ). Finally, according to Labbé, the intestinal loops of the specimen from Mauritius (collected by Mathieu) are of type V. One specimen collected by Mathieu from Mauritius is completely empty inside (MNHN-IM-2000-33687). The loops of the other specimen are of type I (Fig. 9D ), suggesting that it belongs to P. peronii (MNHN-IM-2000-33686).

Lectotype and paralectotypes ( Scaphis viridis ). Australia • lectotype, hereby designated, 50/20 mm; Thursday ( Océanie) [Thursday Island, Torres Strait]; 1892; Lix leg.; MNHN-IM-2000-22964. • 2 paralectotypes, 45/30 mm and 45/25 mm; same collection data as for the lectotype; MNHN-IM-2000-22964. Originally, no jar clearly labeled as the type material of Scaphis viridis was found at the MNHN. However, only one old jar was found at the MNHN with specimens collected from Thursday Island, and the collecting information on the label (specimens collected by M. Lix in 1892) matches the information provided in Labbé’s original description of S. viridis (even though, according to Labbé, the specimens were collected in 1890). The sizes provided by Labbé (48/20, 47/30, and 42/25 mm) match the sizes of the three specimens here and their notum clearly bears dorsal gills, as in the original description of S. viridis . Labbé mentioned four specimens but, given that he provided measurements for only three specimens, it is possible that he only examined three specimens. Or he examined four specimens and one is now missing. The three type specimens are largely destroyed inside (due to Labbé’s dissections). The male parts and radula are missing in both paralectotypes but are still inside the lectotype. The intestinal loops of the lectotype are of type I, with a transitional loop at 5 o’clock (Fig. 80F ). The three types are green (hence the specific name chosen by Labbé) but that color is clearly due to preservation.

Holotype ( Scaphis carbonaria ). New Caledonia • holotype, by monotypy, 40/26 mm; 1880; Réveillère leg.; MNHN-IM-2000-33708. Originally, no jar clearly labeled as the type material of Scaphis carbonaria was found at the MNHN. However, of the several old jars found at the MNHN with specimens collected from New Caledonia, only one matches perfectly the information provided in Labbé’s original description of S. carbonaria : an individual collected in 1880 by M. Réveillère (the French navy officer Paul Réveillère [1829-1905]) with an identification as Peronia . Other jars with specimens from New Caledonia were collected by Fisher in 1878 or by François in 1894. Therefore, it is extremely likely that the specimen collected by Réveillère in 1880 and identified as " Peronia " is the holotype, by monotypy, of Scaphis carbonaria . The size of the holotype (40/26 mm) matches the size provided by Labbé in the original description of S. carbonaria (36/25 mm). Its notum is not well preserved. Dorsal papillae are quite flattened (as pointed out by Labbé) and dorsal eyes cannot be seen, likely because their black color faded. However, dorsal gills are clearly present on the notum. Its intestinal loops are of type I (Fig. 80D ) but its radula is missing. The posterior (female) reproductive parts are still present but poorly preserved. The copulatory parts are missing, except for the muscular sac of the accessory penial gland (approximately 10 mm long) and so the length of the spine of the accessory penial gland cannot be checked (it was not mentioned by Labbé in the original description).

Lectotype and paralectotypes ( Scaphis gravieri ). Mayotte • lectotype, hereby designated, 27/18 mm; 1883; A Vimont leg.; MNHN-IM-2000-33695. Zanzibar • 4 paralectotypes, 30/28, 32/25, 27/23, and 14/10 mm; 1865; Grandidier leg.; MNHN-IM-2000-33693. The type material mentioned in the original description also includes two paralectotypes from Djibouti which could not be located with certainty at the MNHN (see below). Originally, no jar clearly labeled as the type material of S. gravieri was found at the MNHN, but most type material could be traced back.

The original description of S. gravieri is based on seven individuals: two individuals (10/7.5 and 8/6.5 mm) from Djibouti collected by Gravier in 1904; four individuals (32/29 and 30/25 mm) from Zanzibar collected by Grandidier (the French naturalist and explorer Alfred Gandidier [1836-1921]) in 1865; and one individual (28/19 mm) from Mayotte collected by Ach. Vimont in 1883.

One old jar was found at the MNHN with a specimen from Mayotte (MNHN-IM-2000-33695). The information on the label (specimen collected from Mayotte by Vimont in 1883) matches the information provided in Labbé’s original description of S. gravieri , and the specimen size also matches. Therefore, that specimen from Mayotte is here considered to form part of the type series of S. gravieri and designated as the lectotype (MNHN-IM-2000-33695). This lectotype was dissected by Labbé: the radula and the posterior (hermaphroditic) reproductive parts are still in place but the male parts are missing. The intestinal loops are of type I with a transitional loop at 6 o’clock (Fig. 85A ).

Another old jar was found at the MNHN with specimens from Zanzibar (MNHN-IM-2000-33693). The information on the label (specimens collected from Zanzibar by Grandidier in 1865) matches the information provided in Labbé’s original description of S. gravieri , and the specimen size also matches ( Labbé likely provided the size of the largest two specimens). Therefore, those four specimens from Zanzibar are considered to form part of the type series of S. gravieri and are now paralectotypes (MNHN-IM-2000-33693). Only one paralectotype (30/28 mm) from Zanzibar was dissected by Labbé: the radula and the posterior (female) reproductive parts are still in place but the male parts are missing. The intestinal loops are of type I.

The two paralectotypes from Djibouti could not be traced with certainty. There are two old jars of specimens collected by Gravier in 1904 at the MNHN. One jar is labeled with Obock as locality (not Djibouti, even though Obock is in Djibouti) and contains one Peronia specimen of which the size (80/60 mm) does not match Labbé’s original description of S. gravieri . Also, that specimen from Obock is more likely to be a paralectotype of P. gaimardi or a non-type specimen used by Labbé for the re-description of Peronia tongana . The three specimens (70/60, 70/65, and 65/65 mm) of the second jar collected by Gravier in 1904 are from Djibouti (MNHN-IM-2000-33696), which matches perfectly the original description of S. gravieri by Labbé. The problem is that the specimen sizes do not match because Labbé described two individuals of only 10/7.5 and 8/6.5 mm. It is likely that Labbé meant centimeters instead of millimeters (even though he wrote “mm”) because he described a muscular sac of 8 mm in the specimens from Djibouti, which is impossible in individuals that are only 8 and 10 mm long. One of three specimens, possibly dissected by Labbé, possibly is part of the type series of S. gravieri , but it remains questionable. In addition, a specific name was added in pencil on an old label with the number “69” but that name, which is impossible to read, seems to start with a J, and not a G. In summary, it remains unclear whether those three specimens from Djibouti can be regarded as part of the type series of S. gravieri ; however, it ultimately does not matter because a lectotype is designated here.

Syntypes ( Scaphis tonkinensis ). The type material of Scaphis tonkinensis (ten syntypes up to 20/18 mm, according to the original description) could not be located with certainty at the MNHN. Only one old jar was found at the MNHN (MNHN-IM-2000-33700) with specimens collected from Vietnam (as “Tonkin”), and the information on the label (material collected by M. Julien in 1874) matches the information provided in Labbé’s original description of S. tonkinensis . Therefore, it is possible that the jar mentioned here contains the type material of S. tonkinensis . Unfortunately, the jar only contains three pieces of unidentifiable and poorly preserved tissue (each piece measuring approximately 20/10 mm). Two pieces are likely not even part of an onchidiid slug, and it is unclear whether the third piece is part of an onchidiid dorsal notum or not. So, regardless of whether this material is regarded as part of the type material of S. tonkinensis , it is basically useless.

Syntypes ( Scaphis lata ). The type material of Scaphis lata (four syntypes up to 28/28 mm, from Vietnam) could not be located at the MNHN. Only one old jar was found at the MNHN (MNHN-IM-2000-33700) with specimens collected from Vietnam (as “Tonkin”), but the information on the label (specimens collected by M. Julien, in 1874) does not match exactly the information provided in Labbé’s original description of S. lata (specimens collected by M. Julien in 1878), and, instead, matches the information provided in Labbé’s original description of S. tonkinensis (see above).

Lectotype and paralectotypes ( Onchidium durum ). Red Sea • lectotype, hereby designated, 20/15 mm; 1893; Jousseaume leg.; MNHN-IM-2000-33698. • 25 paralectotypes, from 23/15 to 14/14 mm; same collection data as for the lectotype; MNHN-IM-2000-33698. Originally, no jar clearly labeled as the type material of Onchidium durum was found at the MNHN, but it could be traced back. The original description of O. durum is based on “approximately” 20 individuals (from 24/23 to 14/13 mm) from the Red Sea ("Mer Rouge") collected by Jousseaume in 1893.

Several old jars were found at the MNHN with material collected from the Red Sea by Jousseaume. Most jars are labeled with 1892 as collecting date, one jar is labeled with 1893, and another with 1823. The jar with a collecting date of 1893 (MNHN-IM-2000-33678) contains the type series of P. anomala (see above). On the jar with the collecting date of 1823, there is another tiny label with the number “61” (for an unknown numbering system) on which O. durum is clearly written in pencil. It is one of the very few cases in which a species name is indicated for some MNHN material studied by Labbé and there is little doubt that the specimens are the type series of O. durum , especially because the number of individuals and their sizes perfectly match with Labbé’s original description. Clearly, 1823 is a mistake for 1893. Most importantly, contrary to what was described by Labbé, gills are present on the dorsal notum of those individuals. All specimens are poorly preserved. They likely dried at some point and their body is hard. Three specimens were opened by Labbé and are now largely destroyed with only the digestive system inside. A lectotype is designated here in order to clarify the application of O. durum (specimens in the type series could belong to more than one species). Its intestinal loops are not of type II ( Labbé 1934a: 221): they clearly are of type I (Fig. 86C ).

Holotype and paratypes ( Peronia persiae ). Iran - Persian Gulf • holotype [not examined], by original designation, 35 mm; Lavan Island; 26°48.3498'N, 53°16.08'E; Feb 2016; ZSM Mol 20180017. • 2 paratypes [not examined], 22 and 37 mm; same collection data as for the holotype; ZSM Mol 20180018. • 1 paratype [not examined], 32 mm; Bandar Lengeh; 26°33.4833'N, 54°52.8333'E; Mar 2015; ZSM Mol 20180018.

The original description of P. persiae is based on a total of 14 individuals (from 13 to 37 mm): the four types (see above) and ten other specimens from the same two localities as the types. DNA sequences (COI and 16S) are provided for 11 of those 14 individuals, including all four type specimens. However, it is unclear which GenBank sequences correspond exactly to the holotype because this information is missing in GenBank as well as in Maniei et al. (2020a: table 2). It is assumed that the holotype, called "specimen LA7" in Maniei et al. (2020a: table 1), corresponds to the individual called "voucher LaFM7S" in GenBank. Ultimately, it does not matter at all because all mitochondrial sequences of P. persiae cluster together within the unit #4 of P. verruculata : only the COI (MK993404) and the 16S (MK993392) sequences of the "voucher LaFM7S" are included in our phylogenetic analyses to represent P. persiae (Fig. 2 ). Finally, note that the COI and 16S GenBank accession numbers are switched for P. persiae in Maniei et al. (2020a: table 2). Comments on the original description of P. persiae are provided in the species remarks (see below).

Additional material examined

(unit #1). Australia - Queensland • 1 specimen 35/25 mm [2682]; Mackay, Campwin Beach; 21°22.455'S, 149°18.753'E; 5 Jul 2013; TC Goulding and field party leg.; st 121, by boat ramp, mangrove margin with large rocks by creek, Rhizophora and soft mud; MTQ. • 1 specimen 40/25 mm [2620]; Bowen, Dingo Beach; 20°04.864'S, 148°29.576'E; 30 Jun 2013; TC Goulding and field party leg.; st 113, rocky shore nearby a small and dense Rhizophora mangrove patch; MTQ. • 1 specimen 25/15 mm [2622]; same collection data as for the preceding; MTQ. 1 specimen 22/18 mm [1538]; Magnetic Island, near Cockle Bay, off Townsville; 19°10.500'S, 146°49.552'E; 20 Sep 2005; I. Loch leg.; on top of dead coral on fringing reef and muddy sand flats with seagrasses; AM C.448363. • 1 specimen 25/20 mm [2571]; Cairns, Keewara Beach; 16°34.711'S, 145°30.751'E; 18 Jun 2013; TC Goulding and field party leg.; st 102, rocky platform; MTQ.

Indonesia - Ambon • 2 specimens 35/25 mm [2724] and 40/30 mm [2729]; Pulau Haruku; 03°36.31'S, 128°25.04'E; 11 Feb 2014; st 127; M Khalil and field party leg.; rocky Sonneratia mangrove with coral rubble; UMIZ 00162. • 1 specimen 45/30 mm [2856]; Wai; 03°34.65'S, 128°19.53'E; 15 Feb 2014; M Khalil and field party leg.; st 132, narrow band of old Avicennia trees on sandy mud, old logs on ground; UMIZ 00163. - Bali • 1 specimen 20/15 mm [3080]; Gilimanuk; 08°10.26'S, 114°26.61'E; 3 Apr 2014; M Khalil and field party leg.; st 155, large rocks near a patch of Rhizophora ; UMIZ 00164. • 1 specimen 20/12 mm [3115]; Gilimanuk; 08°10.16'S, 114°26.65'E; 4 Apr 2014; M Khalil and field party leg.; st 156, sandy mudflat outside Rhizophora and Avicennia mangrove; UMIZ 00165. - Halmahera • 1 specimen 45/35 mm [5068]; Sofifi; 00°45.47'N, 127°35.90'E; 8 Mar 2015; st 205, Sonneratia mangrove; UMIZ 00166. • 3 specimens 40/25 mm [5120], 50/35 mm [5124], and 35/25 mm [5130]; Folly; 01°14.66'N, 128°10.61'E; 19 Mar 2015; M Khalil and field party leg.; st 217, rocky shore near a beach; UMIZ 00167. - Lombok • 1 specimen 40/25 mm [2987]; Don Don; 08°54.54'S, 116°21.50'E; 26 Mar 2014; M Khalil and field party leg.; st 149, old Avicennia forest with coral rubble; UMIZ 00168. - Seram • 3 specimens 50/40 mm [2868], 50/35 mm [2870], and 55/40 mm [3441]; 02°58.24'S, 128°07.07'E; 18 Feb 2014; M Khalil and field party leg.; st 135, mud next to a mangrove; UMIZ 00169. - Sulawesi • 1 specimen 45/25 mm [2127]; North Sulawesi, Wori; 01°36.06'N, 124°51.73'E; 9 Mar 2013; M Khalil and field party leg.; st 84, old Sonneratia and Avicennia mangrove; UMIZ 00170. • 2 specimens 25/20 mm [2150] and 60/45 mm [2162]; North Sulawesi, Bahoi; 01°43.36'N, 125°01.23'E; 10 Mar 2013; M Khalil and field party leg.; st 85, sand and small rocks outside a mangrove; UMIZ 00171. • 1 specimen 23/18 mm [731]; South East Sulawesi, Walowa, Pasarwajo Bay, Buton Island; 28 Oct 2005; MAE Malaquias leg.; upper tidal, on rock pools; NHMUK 20050628. - Sumatra • 1 specimen 40/30 mm [1747]; Lampung, Penegahan; 05°40.40'S, 105°33.76'E; 18 Oct 2012; M Khalil and field party leg.; st 78, coral rubble on beach exposed to estuary; UMIZ 00172. • 1 specimen 20/15 mm [1759]; Lampung, near Kalianda, Sungai Boluk; 05°40.793'S, 105°33.625'E; 23 Oct 2012; M Khalil and field party leg.; st 82, beach with a few rocks; UMIZ 00173. - Timor • 1 specimen 45/25 mm [5904]; Oesapa; 10°08.73'S, 123°38.10'E; 11 Jul 2016; M Khalil and field party leg.; st 250, sandy part of mangrove, with Sonneratia and Avicennia trees; UMIZ 00174. • 2 specimens 12/7 mm [5925] and 35/20 mm [5927]; Kelapa Lima; 10°08.715'S, 123°36.914'E; 13 Jul 2016; M Khalil and field party leg.; st 252, rocky area at sandy beach with algae; UMIZ 00175.

Japan • 2 specimens 40/30 mm [3752] and 32/25 mm [3751]; Honshu, Wakayama, Nishimuro, near the Seto Marine Biological Laboratory; 33°41.533'N, 135°20.265'E; 2014; T. Nakano leg.; NSMT-Mo 78988.

New Caledonia • 1 specimen 50/45 mm [6202]; Baie de Taaré; 22°15.286'S, 167°00.808'E; 19 Sep 2018; Our Planet Reviewed Koumac 2018 expedition leg.; st KM524, intertidal sandy coral rubble flat in front of mangroves; MNHN-IM-2019-1591. • 1 specimen 73/52 mm [6212]; Tontouta, South side of Page Island (Ubeakure); 22°03.443'S, 166°05.080'E; 25 Sep 2018; Our Planet Reviewed Koumac 2018 expedition leg.; st KM537, coastal rocky mangrove; MNHN-IM-2019-1592. • 1 specimen 43/30 mm [6214]; Pointe Sauveur, Presqu’île de Quano; 21°52.006'S, 165°49.195'E; 26 Sep 2018; Our Planet Reviewed Koumac 2018 expedition leg.; st KM538, muddy intertidal rocky flat in front of mangroves; MNHN-IM-2019-1593.

Palau • 1 specimen 35/30 mm [698]; Ngerchaol Island, East end, South shore, North of quarry on Malakal Island; 07°20.433'N, 134°27.150'E; 15 Feb 1995; K Auffenberg leg.; UF 253871.

Papua New Guinea - Madang • 1 specimen 35/30 mm [5467]; Rempi Area, south Dumduman Island; 05°00.2'S, 145°47.6'E; 9 Nov 2012; MNHN Expedition Papua Niugini leg.; st PM 12, limestone rocky intertidal; MNHN-IM-2013-12008. • 1 specimen 38/30 mm [5468]; same collection data as for the preceding; MNHN-IM-2013-12009. • 1 specimen 35/30 mm [5469]; same collection data as for the preceding; MNHN-IM-2013-12010. - New Ireland • 1 specimen 40/30 mm [6085]; Kavieng, west side of Nago Island; 02°36.3'S, 150°46'E; 6, 9, 10, 14 & 22 Jun 2014; MNHN Expedition Kavieng 2014 leg.; st KM 01; MNHN-IM-2013-50974. • 1 specimen 25/25 mm [6087]; Kavieng, Povalval, East coast of New Ireland; 02°41'S, 150°57'E; 11 & 13 Jun 2014; MNHN Expedition Kavieng 2014 leg.; st KM 05, mixed hard platform and seagrass bed at outlet of rivulet; MNHN-IM-2013-53523. • 1 specimen 30/30 mm [6088]; same collection data as for the preceding; MNHN-IM-2013-53525.

Philippines - Bohol • 2 specimens 40/25 mm [3379] and 35/30 mm [3380]; Maribojoc; 09°44.02'N, 123°47.45'E; 19 Jul 2014; B Dayrat and field party leg.; st 200, coral rubble with sand, at night; PNM 041274. • 2 specimens 30/20mm [3433] and 35/25 mm [3437]; Maribojoc; 09°44.28'N, 123°49.39'E; 20 Jul 2014; B Dayrat and field party leg.; st 202, coral rubble with sand and algae, near Sonneratia ; PNM 041276. - Cebu • 1 specimen 22/15 mm [712]; Badian near Barila, across road from entrance to Children Spring and Kawasan Falls, behind huts; 27 Apr 2005; KNRL-012 leg.; fringing reef flat, 0-2 feet reef walk; UF 368518. - Luzon • 2 specimens 50/35 mm [3160] and 40/25 mm [3161]; Batangas, Lian; 13°59.76'N, 120°37.43'E; 5 Jul 2014; B Dayrat and field party leg.; st 181, sandy, open Avicennia forest, right by the shore; PNM 041277. - Negros • 1 specimen 15/8 mm [704]; San Jose, near Sibulan; 28 Apr 2005; KNRL-011 leg.; exposed rocky intertidal, under and between rocks; UF 368517.

Singapore • 1 specimen 20/15 mm [991]; Pasir Ris Park; 01°22.840'N, 103° 57.224'E; 1 Apr 2010; B Dayrat and SK Tan leg.; st 5, mangrove forest with rich litter, lobster mounds, dead logs, with sand area near the creek; ZRC.MOL.10497.

Vanuatu • 1 specimen 20/10 mm [5480]; Port Vila; ca. 2008; MNHN leg.; MNHN-IM-2013-62392. • 1 specimen 17/11 mm [5481]; same collection data as for the preceding; MNHN-IM-2013-62393.

Vietnam • 2 specimens 60/40 mm [5620] and 40/30 mm [5621]; Hòn Tre Island; 12°11.983'N, 109°18.093'E; 28 Jul 2015; TC Goulding and field party leg.; st 238, coral rubble near small Rhizophora sandy and muddy mangrove; ITBZC IM 00021. • 1 specimen 25/20 mm [5670]; Côn Đ ảo Islands; 08°38.803'N, 106°34.719'E; 22 Jul 2015; TC Goulding and field party leg.; st 235, edge of dense Rhizophora mangrove, near sand; ITBZC IM 00022. • 1 specimen 17/14 mm [5639]; Côn Đ ảo Islands; 08°38.780'N, 106°33.210'E; 23 Jul 2015; TC Goulding and field party leg.; st 236, mangrove patch with many big flat rocks outside; ITBZC IM 00023.

Additional material examined

(unit #2). India • 1 specimen 25/15 mm [1072]; South Andaman, Burman Nala; 11°33.226'N, 92°43.997'E; 8 Jan 2011; B Dayrat and field party leg.; st 53, rocky shore with a patch of Rhizophora , sand and coral rubble but no mud; BNHS 1072. • 1 specimen 10/8 mm [1077]; South Andaman, Corbyn’s Cove; 11°38.676'N, 92°45.005'E; 9 Jan 2011; B Dayrat and field party leg.; st 54, rocky shore only, no mangrove; BNHS 119. • 1 specimen 15/12 mm [1079]; same collection data as for the preceding; BNHS 120. • 1 specimen 30/20 mm [1080]; same collection data as for the preceding; BNHS 121. • 1 specimen 20/15 mm [1081]; same collection data as for the preceding; BNHS 122. • 1 specimen 20/10 mm [1084]; South Andaman, Wandoor; 11°37.140'N, 92°37.242'E; 9 Jan 2011; B Dayrat and field party leg.; st 55, sandy beach with coral rubble; BNHS 117.

Indonesia • 1 specimen 50/35 mm [1746]; Sumatra, Lampung, Penegahan; 05°40.40'S, 105°33.76'E; 18 Oct 2012; M Khalil and field party leg.; st 78, coral rubble on beach exposed to estuary; UMIZ 00178. • 2 specimens 25/20 mm [1741] and 30/22 mm [1742]; same collection data as for the preceding; UMIZ 00179. • 3 specimens 55/35 mm [1796], 50/30 mm [1797], and 45/30 mm [1795]; Sumatra, Lampung, near Kalianda, Sungai Boluk; 05°40.793'S, 105°33.625'E; 23 Oct 2012; M Khalil and field party leg.; st 82, beach with a few rocks; UMIZ 00180.

Additional material examined

(unit #3). Peninsular Malaysia • 1 specimen 35/25 mm [976]; Langkawi; 06°25.361'N, 99°47.269'E; 14 Jul 2011; B Dayrat and field party leg.; st 25, large boulders on sand beach; USMMC 00051. • 3 specimens 35/30 mm [974], 27/20 mm [975], and 30/20 mm [977]; same collection data as for the preceding; USMMC 00064. • 2 specimens 25/20 mm [2546] and 40/25 mm [2547]; Penang, Pasir Panjang, Pulau Betong; 05°17.967'N, 100°11.080'E; 2013; SH Tan leg.; boulders and rocks on a beach; USMMC 00065.

Singapore • 1 specimen 25/20 mm [990]; East Coast Park; 01°18.259'N, 103°55.644'E; 29 Mar 2010; B Dayrat leg.; st 3, rocks of artificial breakwaters; ZRC.MOL.10496. • 1 specimen 12/8 mm [989]; East Coast Park; 01°18.153'N, 103°55.289'E; 29 Mar 2010; B Dayrat leg.; st 2, rocky shore covered by oyster flats; ZRC.MOL.16070.

Additional material examined

(unit #4). India • 1 specimen 55/30 mm [1141]; Mumbai, Bandstand, Bandra; 19°02.863'N, 72°49.174'E; 18 Dec 2011; TC Goulding and field party leg.; st 44, solid rock area, some crevices, near wastewater discharge to ocean; BNHS 22. • 1 specimen 60/40 mm [1143]; same collection data as for the preceding; BNHS 24. • 1 specimen 60/40 mm [1144]; same collection data as for the preceding; BNHS 23.

Pakistan • 1 specimen 50/40 mm [6164]; Sindh Province, Balochistan coast, near Karachi city, Hab River Delta; 24°53.22'N, 66°42.30'E; Apr 2017; S Aslam leg.; on oyster beds; MNHN-IM-2019-1384. • 1 specimen 50/35 mm [6165]; same collection data as for the preceding; MNHN-IM-2019-1385. • 1 specimen 40/25 mm [6166]; same collection data as for the preceding; MNHN-IM-2019-1386.

Additional material examined

(unit #5). Madagascar • 5 specimens 30/25 mm [3140], 40/30 mm [3231], 15/12 mm [3597], 30/20 mm [3142], and 13/8 mm [3598]; Antisiranana (Diego Suarez), Baie Andovobazaha; 12°18.887'S, 49°19.735'E; 16 May 2014; TC Goulding and field party leg.; st 158, rocky platform near Avicennia and Rhizophora mangrove; MNHN-IM-2019-1610. • 5 specimens 50/35 mm [3143], 35/25 mm [3144], 30/20 mm [3146], 30/20 mm [3600], and 30/20 mm [3149]; Ampondrahazo; 12°25.297'S, 49°28.916'E; 20 May 2014; TC Goulding and field party leg.; st 162, sandy mangrove of Bruguiera , on sandy mud in between rocks; MNHN-IM-2019-1611.

Mozambique • 1 specimen 22/18 mm [5507]; Baie de Maputo, Inhaca, Ponta Punduine; 26°02.5'S, 32°53.5'E; 24 Nov 2011; MNHN Expedition Inhaca 2011 leg.; st MM2, tide pools with sand and dead coral rubble; MNHN-IM-2013-62395. • 1 specimen 25/20 mm [5510]; same collection data as for the preceding; MNHN-IM-2013-62398. • 1 specimen 17/13 mm [730]; Cabo Delgado Province, Ibo Island; ca. 12°22'S, 40.35'E; 2 Jul 2006; DG Reid leg.; on mud in seaward Sonneratia zone of mangroves; NHMUK 20080190. • 1 specimen 15/14 mm [733]; Cabo Delgado Province, Ilha Lipulula; 1 km off Mocimboa da Praia; 11°20.65'S, 40°22.95'E; 8 Jul 2006; DG Reid leg.; on beach rock outcrops, upper eulittoral, moderately sheltered shore; NHMUK 20060257.

Additional material examined

(Red Sea). Egypt • 4 specimens 35/25 mm [#1], 40/30 mm [#2], 35/30 mm [#3], and 35/25 mm [#4]; Gulf of Suez, Gimsah Bay, African coast; Mar 1913; Bannwarth leg.; ZMH 27472/4. • 4 specimens from 40/30 mm to 30/25 mm; Suez; Bannwarth leg.; ZMH 27474/4.

Red Sea • 4 specimens from 35/25 mm to 25/22 mm; no precise locality data; Savigny, from the collections of the museum in Marseille, France, leg.; NHMD 90791.

Additional material examined

(historical museum collections). Australia • 1 specimen 30/23 mm; Queensland, Cape York; 1867; Salmin leg.; SMNH 180712. • 1 specimen 30/18 mm; Queensland, Cape York; 1 Jan 1881; Mac Leay leg.; SMNH 180713. • 1 specimen 28/23 mm; Queensland, Palm Island; 1 Jan 1881; Mac Leay leg.; SMNH 180714.

China • 1 specimen 40/28 mm [dissected prior to present study]; Hong Kong; 13 Oct 1878; Salmin leg.; SMNH 180707.

India • 11 specimens 35/28 to 20/15 mm; Nicobar Islands, Sambelong, N. V. Bugt [Great Nicobar, Sambelong, north-west bay (possibly the Ganges Harbor)]; 1 Feb 1846; Reinhardt, Galathea Expedition leg.; NHMD 635300.

Indonesia - Java • 1 specimen 33/25 mm; Batavia [Jakarta]; 06°07'S, 106°48'E; 1890; A Groth leg.; SMNH 180720. • 1 specimen 25/25 mm; Edam Island [Pulau Demar Besar, Jakarta Bay]; 1891; C Aurivillius leg.; SMNH 180719. • 1 specimen 30/28 mm; Insel Mendanao, westlich von Billiton [Mendanau Island, west of Belitung Island, Java Sea]; 20 Sept 1899; C Aurivillius leg.; SMNH 180722. - Tanimbar • 1 specimen 30/26 mm; Jamdena Straits, 2 miles north of Tg Nuan; 07°24'S, 131°19'E; 23 Jun 1970; Mariel King Memorial Expedition Moluccas MV “Pele” 1970 leg.; WAM S26630.

Iran • 14 specimens 80/60 to 25/15 mm; Persian Gulf coast, Bandar Bushehr; 28 Feb 1937; G Thorson leg.; tidevandszonen klippekyst [intertidal rocky shore]; NHMD 635301.

Madagascar • 1 specimen 35/32 mm; Catsepe [Katsepy]; 15°46'S, 46°14'E; 12 May 1912; W Kaudern leg.; SMNH 180724.

Pakistan • 1 specimen 23/20 mm; Karachi; 1884; O Dickson leg.; SMNH 180721.

Singapore • 1 specimen 30/25 mm [dissected prior to present study]; Singapore; 15 Jan 1853; Eugenie Expedition 1851-1853 leg.; st. 1502; SMNH 180716.

Tanzania • 3 specimens 35/25 to 15/14 mm; Zanzibar, Mafia Island, South Juani Island; 29 Jun 1994; M Richmond (from N Yonow’s personal collection) leg.; on film-covered rock at cliff base on exposed cliff to open ocean; MNHN-IM-2014-7989. • 4 specimens 50/35 to 35/25 mm; Zanzibar, Kisakasaka; Jun 1995; M. Richmond (from N Yonow’s personal collection) leg.; on rock outcrops in mangrove channel, very sheltered, in daytime; MNHN-IM-2014-7990.

GenBank sequences.

One COI sequence was obtained from GenBank (MH002601) for an individual identified as Peronia sp. and collected from Singapore ( Chang et al. 2018). This individual as well as others were referred to as a "Singapore clade" by Chang et al. (2018) and clearly belong to the mitochondrial unit #3 of Peronia verruculata (Fig. 2 ). Another COI sequence was obtained from GenBank (MH002570) for an individual identified as Peronia sp. and collected from Singapore ( Chang et al. 2018). This individual as well as others referred to as " Peronia sp. 2" by Chang et al. (2018), following Dayrat et al. (2011), clearly belong to the mitochondrial unit #1 of Peronia verruculata (Fig. 2 ). A third COI sequence was obtained from GenBank (LC390389) for an individual identified as Peronia sp. and collected from Sakurajima, Kagoshima, Japan (Tagaki et al. 2019), which is south to the northernmost known locality near the Seto Marine Biological Laboratory (see material examined). This individual as well as others from "Group V" were referred to as " Peronia sp." by Takagi et al. (2019) and clearly belong to the mitochondrial unit #1 of Peronia verruculata (Fig. 2 ). Four COI sequences were obtained from GenBank (JN543152, JN543153, JN543154, JN543165) for individuals from the coast of China, from Hainan (18°N) to Fujian (26°N) ( Sun et al. 2014). These individuals were referred to as " Peronia verruculata " by Sun et al. (2014) and clearly belong to the mitochondrial unit #1 of Peronia verruculata (Fig. 2 ). Finally, the COI (MK993404) and 16S (MK993392) sequences of the "voucher LaFM7S" represent P. persiae (Fig. 2 ): all published mitochondrial sequences of P. persiae cluster together within the unit #4 of P. verruculata so only one individual is needed to represent P. persiae .

Distribution

(Fig. 6 ). Peronia verruculata is the most widespread of all onchidiid species. Its most western records are known from the Red Sea and southern Mozambique (26°S). Its most eastern records are in Japan, Wakayama (33°N), Vanuatu, and Queensland (21°S). It is unclear how far south it is distributed in southeastern Australia, although we did not find it in Sydney, New South Wales (see remarks below as well as remarks on P. sydneyensis ). Undoubtedly, the delineation and distribution of the mitochondrial units of P. verruculata will change as new DNA sequences are added, especially from the Arabian Sea, the Red Sea, southern India, as well as southeastern Australia (see species remarks). Note that the range of P. verruculata is continuous. Even though our molecular analyses do not include specimens of P. verruculata from places like southern India, the Persian Gulf, or the northwestern corner of the Indian Ocean (coasts of Somalia, Yemen, and Oman), P. verruculata must be present there (red areas in Fig. 6 ). As of today, units #1 and #2 are sympatric in southeastern Sumatra (we found them both together at our stations 78 and 82), and units #1 and #3 are sympatric in Singapore.

Peronia verruculata also is very abundant and has been very often recorded in the past. However, Peronia species are externally cryptic and can be easily misidentified and confused. Here the records that are positively confirmed are distinguished from the records that cannot be confirmed. Erroneous applications of the name P. verruculata (or some of its synonyms) are also listed. All the details can be found in the species remarks (see below).

The presence of P. verruculata is confirmed here at the following locations (as O. verruculatum or P. verruculata , unless specified): Australia, Queensland ( Hoffmann 1928; present study), Torres Strait (type locality of S. viridis ; new record); China ( Sun et al. 2014; Liu et al. 2015; Xu et al. 2018), Hong Kong ( Hoffmann 1928; Britton 1984; present study); India, Andaman Islands (new record), Gulf of Mannar ( Farran 1905), Nicobar ( Mörch 1872a, b, as P. mauritiana ; Semper 1880; Bergh 1884a; present study), western coast (type locality of P. gondwanae ; new record); Indonesia, Ambon (new record), Bali (new record), Halmahera (new record), Java ( Hoffmann 1928; present study), Lombok (new record), Seram (new record), Sulawesi (type locality of O. elberti ; Dayrat et al. 2011, as Peronia sp. 6; new record), Sumatra (new record), Tanimbar (new record), Timor (new record), West Papua (type locality of O. ferrugineum and O. astridae ; new record); Iran, Persian Gulf ( Maniei et al. 2020a, type locality of P. persiae ; present study); Japan, Kagoshima (Tagaki et al. 2019, as Peronia sp.; new record), Wakayama (new record); Madagascar ( Odhner 1919; present study); Malaysia, Peninsular Malaysia (new record); Mayotte (type locality of S. gravieri ; new record); Mozambique ( Dayrat et al. 2011, as Peronia sp. 4 and 5; new record); New Caledonia (type locality of S. carbonaria ; new record); Pakistan ( Hoffmann 1928; present study); Palau (new record); Papua New Guinea, Madang (new record), New Ireland (new record); Philippines ( Labbé 1934a, as P. branchifera ; new record), Bohol (new record), Cebu ( Dayrat et al. 2011, as Scaphis sp.; new record), Luzon (type locality of O. branchiferum ; new record), Negros (new record); Red Sea (type locality of O. verruculatum , P. savignii , P. anomala , and O. durum ; paralectotypes of P. gondwanae ; present study); Singapore ( Hoffmann 1928; Chang et al. 2018; present study); Solomon Islands (type locality of P. gaimardi ; new record); Tanzania, Zanzibar (paralectotypes of S. gravieri ; new record); Vanuatu (new record); Vietnam (type locality of S. lata and S. tonkinensis ; new record).

The following records from the literature are not confirmed here, because authors did not provide enough information supporting the identification (as O. verruculatum or P. verruculata unless specified): Australia ( Hutchings and Recher 1982), New South Wales ( Bretnall 1919; Dakin 1947; Smith and Kershaw 1979); Queensland (Semper 1880; Hedley 1909; Bretnall 1919; Allan and Bell 1947; Allan 1950); Djibouti ( Labbé 1934a, paralectotypes of S. gravieri ); eastern Africa (Semper 1880); India, Andaman Islands ( Santhosh Kumar et al. 2016), Gulf of Kutch ( Menon et al. 1961), Gulf of Mannar (Gopinadha Pillai and Appukuttan 1980), Nicobar ( Plate 1893), northwestern coast ( Mandal and Harkantra 2013; Solanki et al. 2017), Sri Lanka ( Nevill 1870, 1878; Plate 1893), southeastern coast ( Hoffmann 1928), Uran City, near Mumbai ( Patil and Kulkarni 2013); Indonesia, Ambon (Semper 1880; Plate 1893; Martens 1897), Timor ( Martens 1897); Japan ( Nakaoka et al. 2006; Wardiatno et al. 2015), Tokara Islands ( Baba 1958), Misaki ( Baba 1958), Boso Peninsula ( Katagiri and Katagiri 2007); Madagascar ( Marcus and Marcus 1970); Mauritius ( Labbé 1934a), New Caledonia (Fischer and Crosse 1878; Hoffmann 1928; Labbé 1934a); New Guinea ( Labbé 1934a); Philippines (Semper 1880; Labbé 1934a, as P. branchifera and P. verruculata ); Red Sea (Semper 1880; Hoffmann 1928; Labbé 1934a); Samoa ( Schmeltz 1874); South Africa ( Connolly 1939); Vanuatu ( Solem 1959); Vietnam ( Zvonareva and Kantor 2016, as Peronia sp.).

The following records are erroneous, i.e., the names that were used (as O. verruculatum or P. verruculata unless specified) refer to species that are not P. verruculata : Japan, Nagasaki ( Keferstein 1865b) and Sagami Bay ( Hoffmann 1928) are records of P. setoensis ; Djibouti (paralectotype of P. gaimardi ), Red Sea (paralectotype of P. gondwanae ), South Africa ( Hoffmann 1928), and western India (paralectotype of P. gondwanae ; Awati & Karandikar, 1948) are records of P. madagascariensis ; Australia, Northern Territory, Darwin ( Hoffmann 1928) is a record of P. willani ; India, Nicobar Islands ( Mörch 1872a, b), Japan, Tokara Islands ( Baba 1958), and Mauritius (possible paralectotype of P. gondwanae ) are records of P. peronii ; Hawaii ( Hoffmann 1928; Labbé 1934a; Solem 1959) is a record of P. platei . Finally, Britton (1984) recorded from Hong Kong some slugs with intestinal loops of type II as P. verruculata ; those slugs do not belong to Peronia (they likely were Paromoionchis tumidus , a species with intestinal loops of type II).

Etymology.

The etymology of specific names is treated alphabetically. Peronia anomala was named after the supposedly anomalous intestinal loops of type II, except Labbé made a mistake because the intestinal loops are of type I (Fig. 86B ).

Onchidium astridae is named after Astrid of Sweden [1905-1935], spouse of Prince Leopold [1901-1983], King of the Belgians from 1934 to 1951; the type material of O. astridae was collected in 1929 during a scientific journey by Prince Leopold and his wife in the former Dutch East Indies (Indonesia).

Onchidium branchiferum was named after the dorsal gills on the dorsal notum.

Scaphis carbonaria was named after the (artificial) charcoal color ( carbonaria in Latin) of the ventrum of the preserved holotype.

Onchidium durum was named after the hard ( durum in Latin) notum of the preserved type specimens.

Onchidium elberti was named after Dr. J. Elbert, who collected the holotype in 1909.

Onchidium ferrugineum was named after the rusty ( ferrugineum in Latin) color of the live individuals collected by Lesson which belong to two different species: the lectotype belongs to Peronia verruculata (unit #1) and the paralectotypes to Wallaconchis ater . The dorsal notum of some individuals of W. ater can be homogenously of rusty color (e.g., Goulding et al. 2018b: fig. 36F) but individuals of P. verruculata (unit #1) are not typically of rusty color, although their notum commonly displays red patches. Lesson’s (1833: pl. 19, figs 1, 2) illustrations of Peronia ferruginea in his Illustrations de Zoologie represent a Peronia slug with a dorsal notum that is homogenously of rusty color: it almost looks like an individual of Wallaconchis ater to which dorsal gills were artificially added.

Peronia gaimardi was named after Joseph Paul Gaimard [1793-1858], who collected (with Jean René Constant Quoy) the type material in Vanikoro in 1829 during a voyage of the Astrolabe.

Paraperonia gondwanae was named after its supposedly Gondwanan distribution (Red Sea, Mauritius, western India, and Torres Strait).

Scaphis gravieri was named after Charles Joseph Gravier [1865-1937], professor of zoology (worms and crustaceans) at the MNHN, who collected two paralectotypes from Djibouti.

Scaphis lata was named after the broad (lata in Latin) and circular shape of preserved type specimens.

Peronia persiae was named after the Persian Gulf.

Peronia savignii was named after Marie Jules César Lelorgne de Savigny [1777-1851], a French zoologist who participated in Napoleon’s expedition to Egypt and published a plate of illustrations for gastropods (including onchidiids) in the Description de l’Egypte ( Savigny 1817: pl. 2).

Scaphis tonkinensis was named after its type locality in Tonkin, i.e., Vietnam.

Onchidium verruculatum was named after the dorsal notum covered with warts ( verruculatum in Latin).

Scaphis viridis was named after the (artificial) green color of the preserved type specimens.

Habitat

(Figs 65 - 69 ). Unit #1 is found in a large variety of habitats. It is predominantly found on rocks in the rocky intertidal (including man-made structures). It can also be found on huge and isolated boulders on a sandy beach or in coral rubble mixed or not with sand. The rocks on which the unit #1 is found can be associated or not with sparse mangrove trees. It is also found on sandy mud inside or nearby mangroves. Exceptionally, it can be found on old logs inside muddy mangroves. Unit #2 is found on coral rubble and rocks on sandy beaches. Unit #3 is found on rocks on a beach and in the rocky intertidal. Unit #4 is found in the rocky intertidal. Unit #5 is found in the rocky intertidal as well as on mud, sandy or not. There was no habitat data on the labels of the material studied here for unit #6 but it is most likely found in the rocky intertidal, like the other units of Peronia verruculata .

Peronia verruculata is extremely common across its entire distribution. In localities where they overlap geographically, the different mitochondrial units are found more or less in equal abundance (units #1 and #3 in Singapore, and units #1 and #2 in southeastern Sumatra). Peronia verruculata is commonly found during the day, even though a few individuals were also collected at night.

Color and morphology of live animals

(Figs 70 - 77 ). In unit #1, live animals are not covered with mud, but they can often bear tiny pieces of various materials, such as sand and broken shells (Figs 70 - 73 ). The background color of the dorsal notum is highly variable, most often brown (light to dark), or greenish, and occasionally even black. The background is mottled with darker areas, occasionally with red areas. In most animals, the color of the dorsal papillae varies as that of the background itself. In some animals, however, the tip of the dorsal papillae (with and without dorsal eyes) can be bright yellow. The color of the foot is the same as that of the hyponotum, which varies greatly from pure white to dark blue-green. In most animals, the ventral surface is yellowish-greenish or yellowish-bluish. The ventral color (foot and hyponotum) of an individual can change rapidly, especially when disturbed. The ocular tentacles are brown-grey (variable from light to dark), like the head. The ocular tentacles are short (just a few millimeters long). Preserved specimens no longer display the colors of live animals. Colors tend to fade rapidly with preservation.

The dorsal notum of live animals is covered by dozens of papillae of various sizes. Those papillae do not retract within the notum, whether animals are disturbed or not, and so the dorsal notum is never smooth. Larger papillae are not arranged in two longitudinal and lateral ridges (on either side of the median line), even though larger papillae are mostly concentrated in the central area of the dorsal notum. Some papillae bear from one to five black dorsal eyes at their tip (most papillae bear three eyes). The number of papillae with dorsal eyes is variable (from 10 to 22) and papillae in the central area of the dorsum tend to bear more eyes than those on the side. Occasionally, papillae can bear more than five eyes: a central, large papilla can bear up to eight eyes but, like other papillae, is not fully retractable within the notum. The exact number of papillae with eyes can be difficult to count because papillae are often dark, and because the eyes, which are located at the tip of the papillae, can be seen only if papillae are relaxed. Dorsal gills are present on the posterior third of the dorsal notum. Dorsal gills are most easily observed when animals are relaxed under water. When slugs are not under water, dorsal gills are retracted and hard to see. If animals were not relaxed before preservation, gills can be retracted and hard to see in preserved specimens (the best relaxation method is to immerse live specimens in a solution of magnesium chloride).

The color variation in unit #2 (Fig. 74 ) and unit #3 (Fig. 75 ) is similar to the color variation in unit #1, and specimens cannot be separated where units overlap geographically (in Singapore for units #1 and #2, and in southeastern Sumatra for units #1 and #3). The number of papillae with dorsal eyes observed in unit #2 (from 14 to 22) and in unit #3 (from 10 to 18) is within the range observed in unit #1. Slight differences may be due to a more limited sampling.

In unit #4, the color of the dorsal notum is brown, mottled with darker and lighter areas (Fig. 76 ). The ventral surface (foot and hyponotum) is brown-greyish. The number of papillae with dorsal eyes varies from 10 to 18.

In unit #5, the dorsal notum is brown, light to dark, mottled with darker areas (Fig. 77 ). The ventral surface (foot and hyponotum) is yellowish, greenish, or bluish, and can change rapidly in any given individual. The number of papillae with dorsal eyes varies from 10 to 20.

Pictures of live animals were not available for unit #6 (Red Sea). The dorsal color of preserved specimens is beige with faded darker areas. The ventrum is beige. The number of papillae with dorsal eyes varies from 10 to 18, but the black eye color possibly faded in some of them.

The largest specimens are 60 mm long in unit #1, 55 mm long in unit #2, 40 mm long in unit #3, 60 mm long in unit #4, 50 mm long in unit #5, and 40 mm long in unit #6. Exceptionally, one individual in New Caledonia was 73 mm long (unit #1).

External morphology

(Fig. 78A-C ). The body is not flattened. The notum is oval. The hyponotum is horizontal in live animals. The orientation of the hyponotum as well as the shape of the dorsal notum of preserved animals greatly vary depending on preservation. The width of the hyponotum relative to the total width of the ventral surface (pedal sole and hyponotum) varies among individuals but is approximately one third. In the anterior region, the left and right ocular tentacles are superior to the mouth. Eyes are located at the tip of the two ocular tentacles. Inferior to the ocular tentacles, superior to the mouth, the head bears a pair of oral lobes. The latter are smooth, with no transversal protuberance. The male opening (of the copulatory complex) is below and to the left of the right ocular tentacle (i.e., between the two ocular tentacles, but closer to the right than to the left tentacle). The anus is posterior, median, close to the edge of the pedal sole. On the right side (to the left in ventral view), a peripodial groove is present at the junction between the foot and the hyponotum, running longitudinally all the way from the head to the posterior end. The female pore, which marks the posterior end of the peripodial groove, is located a few millimeters from the anus and the pneumostome, which does not vary much among individuals. The pneumostome is median. Its position on the hyponotum relative to the notum margin and the edge of the pedal sole varies among individuals but averages in the middle.

Visceral cavity and pallial complex.

The anterior pedal gland is small, more or less round, and flattened, lying on the floor of the visceral cavity below the buccal mass and below a thin layer of connective tissue (it can be hard to detect). The heart, enclosed in the pericardium, is on the right side of the visceral cavity, slightly posterior to the middle. An anterior vessel supports several anterior organs such as the buccal mass, the nervous system, and the copulatory complex. The kidney is nearly symmetrical, the right and left parts being equally developed. The kidney is intricately attached to the respiratory complex. The lung is posterior in two more or less symmetrical parts, left and right, which are joined in the middle.

Nervous system

(Fig. 78D ). The circum-esophageal nerve ring is post-pharyngeal and pre-esophageal. The paired cerebral ganglia are separated by a short cerebral commissure of which the length varies among individuals. Paired pleural and pedal ganglia are also all distinct. The visceral commissure is short but distinctly present and the visceral ganglion tends to be slightly to the left. Cerebro-pleural and pleuro-pedal connectives are short and pleural and cerebral ganglia touch each other on either side. Nerves from the cerebral ganglia innervate the buccal area and the ocular tentacles and, on the right side, the penial complex. Nerves from the pedal ganglia innervate the foot. Nerves from the pleural ganglia innervate the lateral and dorsal regions of the mantle. Nerves from the visceral ganglia innervate the visceral organs. Ganglia are commonly surrounded by almost transparent connective tissue through which they can be observed.

Digestive system

(Figs 79 - 81 , 82A , 83A , 84A, B , 85 - 93 ). There are no jaws. The left and right salivary glands, heavily branched, join the buccal mass dorsally, on either side of the esophagus. The esophagus is narrow and straight, with thin internal folds. The esophagus enters the stomach anteriorly (Fig. 79 ). Only a portion of the posterior aspect of the stomach can be seen in dorsal view because it is partly covered by the lobes of the digestive gland. The dorsal lobe is mainly on the right. The left, lateral lobe is mainly ventral. The posterior lobe covers the posterior aspect of the stomach. The stomach is a U-shaped sac divided into four chambers (Fig. 79 ). The first chamber, which receives the esophagus, is delimited by thin tissue, and receives the ducts of the dorsal and lateral lobes of the digestive gland. It is internally smooth (with no ridges). The second, posterior chamber, delimited by thick muscular tissue (which takes most of the space inside), receives the duct of the posterior lobe of the digestive gland. The third, funnel-shaped chamber is delimited by thin tissue with high leaflet-like ridges internally. The fourth chamber is continuous and externally similar to the third, but it bears only low, thin ridges internally.

The intestine is long and narrow. Intestinal loops were checked in every specimen listed in the material examined: the intestinal loops are of type I with a transitional loop oriented between 3 and 6 o’clock (Figs 79 - 81 , 82A , 83A , 84A, B , 85 , 86 ). There is no rectal gland.

The radula is in between two large postero-lateral muscular masses (Figs 87 - 93 ). Each radular row contains a rachidian tooth and two half rows of lateral teeth of similar size and shape. Examples of radular formulae are presented in Table 5 . The rachidian teeth are unicuspid (Fig. 87A ): the median cusp is always present; there are no conspicuous cusps on the lateral sides of the base of the rachidian tooth. The median cusp of the rachidian teeth is approximately 40 μm long. The lateral aspect of the base of the rachidian teeth is straight. The half rows of lateral teeth form an angle of 45° with the rachidian axis. Except for the few innermost and few outermost lateral teeth, the size and shape of the lateral teeth do not vary along the half row, nor do they vary among half rows. The lateral teeth are unicuspid with a flattened and curved hook (approximately from 80 to 120 μm long) with a rounded tip, but there is also a pointed spine on the outer lateral expansion of the base, or basal lateral spine (Fig. 87D ). In most cases, the basal lateral spine cannot be observed because it is hidden below the hook of the next, outer lateral tooth. It can only be observed when the teeth are not too close (such as in the innermost and outermost regions) or when teeth are placed in an unusual position. The inner and outer lateral aspects of the hook of the lateral teeth are straight (i.e., not wavy and not with any protuberance).

Reproductive system

(Figs 82B, C , 83B, C , 84C, D , 94 - 109 ). Sexual maturity is correlated with animal length. Mature individuals have large female organs (with a large female gland mass) and fully developed male copulatory parts. The smallest, immature individuals may have inconspicuous (or no) female organs and rudimentary anterior male parts.

The female organs are located (with some male parts) at the posterior end of the visceral cavity (Figs 82B , 83B , 84C , 94A-C , 95A, B , 96A ). The hermaphroditic gland is a single mass, joining the spermoviduct through the hermaphroditic duct (which conveys the eggs and the autosperm). There is a narrow, elongated receptaculum seminalis (caecum) along the hermaphroditic duct. The female gland mass contains various glands (mucus and albumen) which can hardly be separated by dissection and of which the exact connections remain uncertain. The hermaphroditic duct becomes the spermoviduct (which conveys eggs, exosperm, and autosperm). Proximally, the spermoviduct is not divided (at least externally) and is embedded within the female gland mass. Distally, the spermoviduct branches into the straight deferent duct (which conveys the autosperm up to the anterior region, running through the body wall) and the oviduct. The free oviduct conveys the eggs up to the female opening and the exosperm from the female opening up to the fertilization chamber. The large, spherical-ovate spermatheca connects to the oviduct through a short duct. The oviduct is narrow and straight. There is no vaginal gland.

The male anterior organs consist of the penial complex (penis, penial sheath, vestibule, deferent duct, retractor muscle) and the accessory penial gland (Figs 82C , 83C , 84D , 94D , 95C , 96B , 97 - 109 ). The penial complex and the accessory penial gland share the same vestibule and the same anterior male opening.

The penial sheath is narrow and elongated. The penial sheath protects the penis for its entire length. The beginning of the retractor muscle marks the separation between the penial sheath (and the penis inside) and the deferent duct, which is highly coiled. The retractor muscle, which can be shorter or longer than the penial sheath, inserts at the posterior end of the visceral cavity. Inside the penial sheath, the penis is a narrow, elongated, soft, hollow tube. Its distal end bears conical hooks which are less than 50 μm long in units #1 and #2, less than 55 μm long in units #5 and #6, and less than 60 μm in units #3 and #4 (Figs 97 - 102 ). When the penis is retracted inside the penial sheath, the hooks are densely packed inside the tube-like penis; during copulation, the penis is evaginated like a glove and the hooks are outside, not as densely packed. In some individuals of unit #4, a few penial hooks are exceptionally double, or two-pronged (Fig. 100C ).

The accessory penial gland is a long, tube-like flagellum with a proximal dead end. The length of the flagellum of the penial gland varies among individuals but it is always highly coiled. Near its distal end (just before the hollow spine), the flagellum is enlarged into a thick muscular sac, which is less than 15 mm long in units #1 and #6 and less than 10 mm long in the other units. Distally, the flagellum ends in a hard, hollow spine protected by a sheath which opens into the vestibule.

The hollow spine is narrow, elongated, conical at its base, and straight or slightly curved (Figs 103 - 109 ). Its shape varies between individuals, including at its tip which may or may not be pointed. Its length (Table 4 ) ranges from 1.4 mm ([5481] MNHN-IM-2013-62393) to 2 mm ([5068] UMIZ 00166, [5469] MNHN-IM-2013-12010) in unit #1, from 1.4 mm ([1796] UMIZ 00180) to 1.7 mm ([1797] UMIZ 00180) in unit #2, from 1.8 mm ([990] ZRC.MOL.10496) to 2.2 mm ([976] USMMC 00051) in unit #3, from 2.2 mm ([6165] MNHN-IM-2019-1385) to 2.8 mm ([6164] MNHN-IM-2019-1384) in unit #4, from 1.8 mm ([3144] MNHN-IM-2019-1611) to 2 mm ([3231] MNHN-IM-2019-1610) in unit #5, from 2 mm (ZMH 27472, spm #4) to 2.4 mm (ZMH 27472, spm #2).

Its diameter at the base (Table 4 ) ranges from 100 μm ([5481] MNHN-IM-2013-62393) to 200 μm ([5621] ITBZC IM 00021) and even, exceptionally, 270 μm ([991] ZRC.MOL.10497) in unit #1, from 140 μm [1796] UMIZ 00180) to 160 μm [1797] UMIZ 00180) in unit #2, from 200 μm ([989] ZRC.MOL.16070) to 270 μm ([977] USMMC 00064) in unit #3, around 200 μm ([6164] MNHN-IM-2019-1384, [6165] MNHN-IM-2019-1385, and [6166] MNHN-IM-2019-1386) in unit #4, from 150 μm ([3144] MNHN-IM-2019-1611) to 180 μm ([3231] MNHN-IM-2019-1610) in unit #5, and from 140 μm (ZMH 27472, spm #4) to 200 μm (ZMH 27472, spms #2 and #3) in unit #6.

Its diameter at the tip (Table 4 ) ranges from 35 μm ([5481] MNHN-IM-2013-62393) to 50 μm (e.g., [5068] UMIZ 00166) in unit #1, from 30 μm [1795] UMIZ 00180) to 35 μm [1796] UMIZ 00180) in unit #2, and from 40 μm [989] ZRC.MOL.16070) to 80 μm [977] USMMC 00064) in unit #3, around 50 μm ([6164] MNHN-IM-2019-1384, [6165] MNHN-IM-2019-1385, and [6166] MNHN-IM-2019-1386) in unit #4, from 45 μm ([3231] MNHN-IM-2019-1610) to 50 μm ([3144] MNHN-IM-2019-1611) in unit #5, and from 55 μm (ZMH 27472, spm #1) to 60 μm (ZMH 27472, spms #2 to #4) in unit #6.

Diagnostic features

(Table 4 ). Externally, Peronia verruculata cannot be distinguished from the other Peronia species. The animal length, which is helpful to identify P. peronii , does not help identify P. verruculata . In our material, most live animals are between 30 and 40 mm long, but some animals are exceptionally longer: e.g., 60 mm for [2162] (UMIZ 00171) in Sulawesi, 60 mm for [5620] (ITBZC IM 00021) in Vietnam, and 73 mm for [6212] (MNHN-IM-2019-1592) in New Caledonia. Internally, all units of P. verruculata are cryptic with each other (Table 4 ). The ranges of sizes for the accessory penial gland (length, diameter at base, diameter at tip) overlap when all units are considered, but ranges may differ when only a pair of units is considered (e.g., the accessory penial gland spine is shorter than 160 μm in unit #2 and longer than 200 μm in unit #3).

The units #1 and #3 are sympatric in Singapore but they cannot be always separated anatomically. Based on the length of its spine (270 μm), the Singapore individual [991] would be assigned to the mitochondrial unit #3 because the spine is longer than 200 μm in unit #3 while it usually is less than 200 μm in unit #1, but it belongs to the mitochondrial unit #1 (Fig. 2 ). The diameter of the tip of the spine only partly overlaps between unit #1 (from 35 to 50 μm) and unit #3 (from 40 to 80 μm), but that trait is hardly practical when it comes to identification (it requires SEM). The units #1 and #2 are sympatric in Sumatra (we found them both together at the stations 78 and 82) but they cannot be separated because they are completely cryptic anatomically (Table 4 ). All that is not to say that there are no anatomical differences between units of P. verruculata . On average, the diameter of the spine of the accessory penial gland tends to be larger both at the base and at the tip in unit #3. However, because ranges of variation overlap, anatomical traits cannot be used to reliably assign individuals to any particular unit.

Peronia verruculata is close anatomically to P. sydneyensis and P. willani . They all share intestinal loops of type I with a transitional loop oriented between 3 and 6 o’clock. There are, however, important differences. The muscular sac of the accessory penial gland is significantly longer in P. willani (up to 25 mm) than in P. verruculata (up to 15 mm); the spine of the accessory penial gland is significantly shorter in P. sydneyensis (less than 1 mm) than in P. verruculata (at least 1.3 mm); strong, hemispherical protuberances cover the spine in all individuals of P. sydneyensis and are absent in all other species. Peronia sydneyensis and P. verruculata cannot be confused even where they are sympatric (Queensland and New Caledonia) and Peronia verruculata and P. willani are not sympatric based on current data.

Remarks.

Species delineation. Our decision of recognizing a single species with high population structure and several mitochondrial units is explained in the results (see species delineation). Fresh material from the Red Sea, Somalia, Yemen, Oman, and the Persian Gulf is needed to determine the relationships between the populations of P. verruculata from the Red Sea and the remainder of the species. Similarly, fresh material is needed from southwestern and southeastern India, including Sri Lanka, to determine the relationships between the western (Indian Ocean) and eastern (South-East Asia and West Pacific) populations. Most likely, additional populations will show that mitochondrial units are even more mixed than what is already shown here, and new units may be found. Nuclear markers will remain indispensable as the current data show that populations that seem divergent using mitochondrial markers are not reproductively isolated. It is not excluded that populations from the Red Sea belong to two distinct species (both with intestinal loops of type I): P. verruculata and another species endemic to the Red Sea. The Peronia diversity in the Red Sea would thus be similar to what is found in Japan, which is also at the periphery of the distribution of Peronia (Fig. 6 ).

Synonymy. The application of all the species names regarded as junior synonyms of P. verruculata is addressed here, following a chronological order starting with P. verruculata (Tables 1 , 6 ).

Based on our data, there are two Peronia species in the Red Sea, one characterized by intestinal loops of type I (with a transitional loop oriented between 3 and 6 o’clock) and the other characterized by intestinal loops of type V (see remarks on P. madagascariensis ). Because the intestinal loops of the lectotype of O. verruculatum are of type I (Fig. 86A ), P. verruculata applies to the species described here with intestinal loops of type I.

The original description of Onchidium ferrugineum was published four times in different venues by Lesson, twice in 1831 (first in the Bulletin des sciences naturelles and then in the zoology section of the Coquille voyage), once in February 1832 (in the Mémorial encyclopédique), and once again in 1833 (in his Illustrations de Zoologie ). According to Cretella (2010), the date of publication for the description of O. ferrugineum in the Coquille voyage is November 15, 1831. Therefore, the oldest and original description of O. ferrugineum is the one published in the Bulletin des sciences naturelles in April 1831. Both descriptions from 1831 did not include any illustration. An illustration of an animal ventral view was published by Lesson (1832: 36-37, fig. 32) in the Mémorial encyclopédique. Two beautiful, colored pictures were published in Lesson’s (1833: pl. 19) Illustrations de Zoologie .

The type locality (of the lectotype) of Onchidium ferrugineum is Manokwari, West Papua, Indonesia, where at least three Peronia species are known to be present (Fig. 6 ). Based on the length of the lectotype (35 mm) and its intestinal loops of type I with a transitional loop at 4 o’clock (Fig. 80A ), Onchidium ferrugineum applies to the species described here ( P. verruculata ) and not to P. griffithsi or P. peronii (Table 4 ). Unfortunately, this identification cannot be confirmed by the muscular sac or the spine of the accessory penial gland, which are missing in the lectotype. Labbé (1934a: 213-216) claims that there is no accessory penial gland in Onchidium ferrugineum and thus does not comment on the spine and the muscular sac of the accessory penial gland of the lectotype. It is unclear whether Labbé dissected the lectotype or if he found it already dissected by Lesson (who commented on the penis of the paralectotypes and thus might have dissected the lectotype as well). Eleven dorsal papillae with eyes were counted on the lectotype, but it is possible that others faded with time.

Lesson (1833: pl. 19) transferred Onchidium ferrugineum to Peronia . In the written description, Lesson (1833: unnumbered page) considered Peronia ferruginea the type of a genus which he decided to call Peronia , following Blainville, but the type species of Peronia is O. peronii , by monotypy, and the author of Peronia is Fleming (1822a, b). Oken (1834b: 269-270) reported Peronia ferruginea from Lesson’s (1833: pl. 19) Illustrations de Zoologie . Van der Hoeven (1850: 786; 1856: 817) suggested, based on Lesson’s (1833: pl. 19) own illustration, that Peronia ferruginea may be a nudibranch instead of an onchidiid, but there is no question that Peronia ferruginea applies to an onchidiid species. Gray (1850: 117), Adams and Adams (1855: 235), and Tapparone Canefri (1883: 214) classified O. ferrugineum in Peronia but other authors preferred the original combination with the generic name Onchidium .

Semper (1882: 268) kept O. ferrugineum in Onchidium and regarded it as a questionable name because he (erroneously) thought that its original locality was unknown. Plate (1893) did not comment on it. Bretnall (1919: 326-327) thought that O. ferrugineum referred to a species insufficiently known and merely repeated Lesson’s original description. Bretnall (1919: 326) also suggested that O. ferrugineum seemed "closely related to that of M. de Blainville," i.e., Peronia mauritiana , a synonym of P. peronii . Solely based on information from the original description, Hoffmann (1928: 71, 74) regarded O. ferrugineum as a junior synonym of O. verruculatum and disagreed with Bretnall that it could refer to O. peronii . However, the application of O. ferrugineum cannot be deduced from the original description, especially because it is based on Peronia and Wallaconchis specimens (see above the remarks on the type material). Finally, Labbé (1934a: 213-216), who re-examined the type specimens of O. ferrugineum , created the generic name Lessonia (later replaced by Lessonina ) for O. ferrugineum , for a genus characterized by a unique combination of traits (large and coiled penis, dorsal gills, etc.), without realizing that the types of O. ferrugineum were part of two species from two different genera.

Peronia savignii is an objective junior synonym of Onchidium verruculatum because they share the same lectotype (see above, the remarks on the type material of Peronia savignii ). Hoffmann (1928: 69, 72), Labbé (1934a: 193), and Dayrat (2009: 16) all regarded Onchidium savignyi Semper, 1800 as an emendation of Peronia savignii Récluz, 1869, and Onchidium savignyi as a junior synonym of O. verruculatum . However, Onchidium savignyi Semper, 1880 is not an emendation of Peronia savignii Récluz, 1869. Semper (1880: 260-261, pl. 19, fig. 6, pl. 20, fig. 1, pl. 22, figs 5-9) created Onchidium savignyi as a new name for two individuals from Bohol, Philippines. Semper (1880: 260) merely suggested (with a question mark) that his Onchidium savignyi might refer to the same species as " O. Peronii Savigny, Description de l’Egypte,” but did not even mention the existence of Peronia savignii . One syntype of Onchidium savignyi is well preserved and still undissected (ZMB/Moll 39018). Its notum bears gills, which agrees with Semper’s original description and means that Onchidium savignyi refers to a Peronia species. Therefore, Peronia savignyi (Semper, 1880) is a secondary junior homonym of Peronia savignii Récluz, 1869 because ICZN Article 58 applies ( savignyi and savignii are deemed to be identical spellings). As junior secondary homonym, Peronia savignyi is an available but subjectively invalid name ( ICZN 1999: Article 57.3) (Tables 1 , 6 ).

Some authors ( Hoffmann 1928: 72-74; Labbé 1934a: 193; Connolly 1939: 454) regarded Onchidium savignyi as a junior synonym of O. verruculatum , while others regarded Onchidium savignyi as valid (e.g., Connolly 1912: 225; Collinge 1910: 172). Also, Onchidium savignyi Semper has naturally caused some confusion with respect to whether it refers to the same species as Peronia savignii Récluz (e.g., Fischer and Crosse 1878: 697; Smith 1903: 401). Strangely enough, the situation is simple: Peronia savignii Récluz is objectively invalid (as junior objective synonym of O. verruculatum ) and Peronia savignyi (Semper) is subjectively invalid (as junior secondary homonym O. savignii ). Semper’s description of the two specimens of O. savignyi from Bohol seems to suggest that they belong to P. verruculata (e.g., retractor muscle attaching to the end of the body cavity, accessory penial gland spine 2.5 mm long), but the long muscular sac (22 mm long) matches better the anatomy of P. peronii (Table 4 ).

The two syntypes of Onchidium branchiferum are from Manila, Luzon, Philippines. Anatomical traits described by Plate (insertion of the retractor muscle of the penis at the end of the visceral cavity, spine of the accessory penial gland 1 mm long) indicate that O. branchiferum applies to P. verruculata , even though they cannot be confirmed on the syntypes in which all internal organs are either missing or destroyed (Table 4 ). Plate did not draw the intestinal loops but he describes them as being type I (the orientation of the transitional loop is unknown). The number of radular teeth per half row (88) also matches what is known in P. verruculata (Table 5 ). According to Plate (1893: 184), O. branchiferum is easily recognizable because its branchial plumes are only present on the posterior end of the dorsum (posterior sixth). However, this trait is not distinct from other species and varies depending on preservation (gills are often retracted in preserved specimens and can only be observed if specimens were carefully relaxed before preservation). Plate (1893) did not provide any other feature supporting O. branchiferum as a distinct species, and he did not compare it with any other existing species. Onchidium branchiferum is regarded here as a new junior synonym of P. verruculata (Tables 1 , 6 ).

Hoffmann (1928: 75) listed Onchidium branchiferum as a valid name (solely based on information from the original description) but considered it to refer to a "local form" of O. verruculatum . Labbé (1934a: 194) transferred Onchidium branchiferum to Peronia and regarded P. branchifera as a valid name "out of deference to the eminent zoologist Ludwig Plate" even though he agreed with Hoffmann that P. branchifera most likely was just a local form of P. verruculata . Labbé’s re-description of P. branchifera was based on a specimen (30/23 mm) collected by Ach. Cuming in 1844 from an unknown locality in the Philippines. There are two jars preserved at the MNHN with Peronia specimens collected by Ach. Cuming in 1844. Labbé (1934a: 192-194) also re-described a specimen collected from the Philippines by Ach. Cuming in 1844 as P. verruculata . It is not possible to determine which jar corresponds to what species in Labbé’s (1934a) monograph because Labbé did not indicate species identifications for any of the MNHN specimens he examined. Labbé’s description of a "short penial gland" indicate that he most likely examined P. verruculata (unit #1). Finally, Marcus and Marcus (1970: 213) wrote that P. branchifera was close to P. verruculata but with no explanation.

Onchidium elberti was described by Simroth (1920) from Muna Island, southeastern Sulawesi, Indonesia, where only Peronia verruculata is known to be present (Fig. 6 ). Internal features of the holotype (24 mm long) are fully compatible with the anatomy of P. verruculata : intestinal loops are of type I with a transitional loop oriented at 5 o’clock (Fig. 80B ) and the muscular sac of the accessory penial gland is 8 mm long (Table 4 ). Eleven papillae with dorsal eyes were counted (which fits within the range of the species) but some may have faded with time. As a result, Onchidium elberti is regarded here as a junior synonym of Peronia verruculata (Tables 1 , 6 ). Hoffmann (1928: 71, 75) thought Onchidium elberti was a junior synonym of O. verruculatum , based on information from Simroth’s original description.

Onchidium astridae , the type species of Labbé’s genus Scaphis , was originally described by Labbé (1934b) within the genus Onchidium . Only one specimen is known, the holotype (20/18 mm) by monotypy, from Sorong, West Papua, Indonesia. There is no doubt that Onchidium astridae applies to a Peronia species because the dorsum of the holotype bears gills. All copulatory parts are missing and Labbé did not describe the length of the muscular sac or the length of the spine of the accessory penial gland. Labbé (1934a: 213, fig. 46) described two muscular sacs instead of just one, but that could not be confirmed here. At least three Peronia species are present in West Papua (Fig. 6 ). However, given the size of the holotype (20 mm long) and, importantly, its intestinal loops of type I with a transitional loop at 4 o’clock (Fig. 80C ), Onchidium astridae is regarded as a junior synonym of P. verruculata (Tables 1 , 4 , 6 ). Note that the number of papillae with dorsal eyes could not be counted on the preserved holotype. According to Labbé (1934b), Onchidium astridae is close to Onchidium vaigiense and O. steenstrupi , but both names refer to Marmaronchis vaigiensis , a species which belongs to a distinct genus ( Dayrat et al. 2018).

The original description of Peronia gaimardi was based on two specimens from Vanikoro, Solomon Islands, which were found at the MNHN, and one specimen from Djibouti, which could not be located. The type locality is Vanikoro, locality of the lectotype designated in the present study. Our molecular data demonstrate that Peronia verruculata (unit #1) is present in Vanikoro, but P. peronii and P. platei could also be found there (Fig. 6 ). Given the intestinal loops of type I (with a transitional loop at 5 o’clock) observed in the lectotype (Fig. 80F ), P. gaimardi is regarded as a synonym of P. verruculata (Tables 1 , 4 , 6 ). The male parts of the lectotype are missing and Labbé’s description of the copulatory apparatus is confusing because it is based indiscriminately on individuals from both Vanikoro and Djibouti. His measurement of the spine of the accessory gland (8 mm long) is most likely a mistake. In the present study, the longest spine (5 mm long) was found in the lectotype of P. fidjiensis (a synonym of P. peronii ) from Fiji. Also, the lectotype of P. gaimardi only is 44 mm long, which would make it a very small individual of P. peronii . Given the large size (80 mm long, according to Labbé) of the paralectotype from Djibouti, it most likely belongs to P. madagascariensis , a species present there, and for which large specimens are known (Table 4 ). It would imply that Labbé confused its intestinal loops of type V for a type I, which is a mistake he often made. Marcus and Marcus (1970: 214) wrote that P. gaimardi might be a junior synonym of P. verruculata based on information from the original description.

Peronia anomala , originally described from the Red Sea, is regarded as a junior synonym of P. verruculata because, contrary to what Labbé indicated in the original description, Peronia anomala is characterized by intestinal loops of type I (Fig. 86B ). It is assumed in this work that there is only one species of Peronia slugs with intestinal loops of type I in the Red Sea, although fresh material from the Red Sea may show that there is more than one species. Marcus and Marcus (1960: 881) suggested that P. anomala could be a synonym of P. verruculata and that intestinal loops of both types I and II are found in P. verruculata , but intestinal loops are only of type I in P. verruculata and there are no intestinal loops of type II in Peronia . Maniei et al. (2020a: table S1) took Labbé’s description for granted and considered that P. anomala was characterized by intestinal loops of type II.

The type specimens used by Labbé for the original description of Paraperonia gondwanae belong to several species, because our data show that slugs with intestinal loops of types I and V necessarily belong to distinct species. The application of the name Paraperonia gondwanae is determined by the lectotype from Bombay (MNHN-IM-2000-33681) with intestinal loops of type I (Fig. 84A ). Paraperonia gondwanae applies to P. verruculata , and, more specifically, to the populations of the mitochondrial unit #4 from western India and Pakistan (Fig. 6 , Tables 1 , 6 ). The paralectotypes from the Red Sea with intestinal loops of type I also belong to P. verruculata : one " e " paralectotype from the Red Sea (MNHN-IM-2000-33688), and two " d " paralectotypes from Suez (MNHN-IM-2000-33684). The paralectotypes with intestinal loops of type V belong to P. madagascariensis : one of the " a " paralectotypes from Bombay (MNHN-IM-2000-33682) and one of the " c " paralectotypes from Suez (MNHN-IM-2000-33683). The large specimen with intestinal loops of type I from Mauritius (MNHN-IM-2000-33686), which may or may not be part of the type material of P. gondwanae , likely belongs to P. peronii .

Scaphis viridis was described by Labbé based on three syntypes (four according to the original description) from Thursday Island, in the Torres Strait, Australia. The presence of P. verruculata in the Torres Strait is not demonstrated positively with fresh material. However, P. verruculata is the only species we found in northeastern Queensland (up to Cairns, 16°S). None of the Peronia slugs we collected north of Bowen (20°S) were individuals of P. sydneyensis which is thought to be only distributed from southern Queensland down to New South Wales (Sydney) and eastwards to New Caledonia. More importantly, both the original description ( Labbé 1934a: 207-208, figs 31-34) and the traits examined in the lectotype here confirm that S. viridis applies to P. verruculata (Table 4 ): intestinal loops of type I with a transitional loop at 5 o’clock (Fig. 80F ; Labbé 1934a: fig. 32), muscular sac of the accessory penial gland 14 mm long ( Labbé) and 15 mm long (lectotype), spine of the accessory penial gland 1 mm long ( Labbé) and 1.7 mm long (lectotype), retractor muscle attaching at the posterior end of the visceral cavity. Because those traits are only compatible with the anatomy of P. verruculata , S. viridis is regarded here as a junior synonym of P. verruculata and which applies to the unit #1 (Tables 1 , 6 ). Finally, a total of 13 dorsal papillae with eyes was observed in the lectotype; more may have faded with time. Labbé only compared S. viridis with Peronia acinosa , a nomen dubium which may or may not refer to an onchidiid species (see general discussion).

There are three Peronia species in New Caledonia, the type locality of Scaphis carbonaria (Fig. 6 ). DNA sequences of individuals from New Caledonia belong to two species in our molecular data set ( P. verruculata and P. sydneyensis ). Although our molecular data do not include any specimen of P. peronii from New Caledonia, it is present there based on the rest of its distribution (it is found all the way to Fiji and Tonga; Fig. 6 ) and on an old specimen from a historical museum collection (ANSP 203028). Two characters in Labbé’s original description are problematic. The penis, described as "wide and short, without hooks" ( Labbé 1934a: 209, our translation), is absolutely incompatible with Peronia , in which the penis is thin, elongated, and always with hooks in the distal region. The absence of dorsal eyes on the notum is also quite perplexing. The notum of the holotype is in poor condition and its dorsal eyes cannot be seen, likely because their black color faded. However, dorsal gills are clearly present on the notum and there is no doubt that S. carbonaria applies to a Peronia species. Based on the length of the muscular sac of the penial accessory gland (10 mm), S. carbonaria is not a junior synonym of P. peronii . However, its muscular sac and its intestinal loops of type I with a transitional loop oriented at 4 o’clock are compatible with both P. verruculata and P. sydneyensis (Table 4 ). The length of the spine helps distinguish both species but Labbé did not mention it and it is missing in the holotype. Therefore, strictly speaking, S. carbonaria should be regarded as a nomen dubium. However, because there are many older names available for the unit #1 of P. verruculata (Table 6 ), S. carbonaria can be regarded as another junior synonym of P. verruculata . It would make no sense to apply it to P. sydneyensis because several important organs (the penis, the spine of the penial accessory gland, the radula) are missing in the holotype and because Labbé’s original description is problematic and incomplete.

Scaphis gravieri was described originally based on types from Mayotte, Zanzibar, and Djibouti. The application of Scaphis gravieri is now based on the lectotype from Mayotte (MNHN-IM-2000-33695), with intestinal loops of type I (Fig. 85A ). Our data do not include fresh material from Mayotte, but Mayotte is located between Madagascar and Mozambique where P. verruculata (unit #5) is present. Therefore, S. gravieri is regarded as a junior synonym of P. verruculata (Tables 1 , 4 , 6 ). Note that P. madagascariensis , a distinct species with intestinal loops of type V, also is expected to be present in Mayotte, even though it has not been recorded there so far (Fig. 6 ). The presence of P. verruculata in Zanzibar (locality of some paralectotypes of S. gravieri ) is possible but needs to be confirmed with fresh material. Additional, non-type specimens from Zanzibar were examined (MNHN-IM-2014-7989, MNHN-IM-2014-7990): their intestinal loops are of type I with a transitional loop at 5 o’clock. Therefore, those specimens cannot belong to P. madagascariensis (intestinal loops of type V) or P. peronii (intestinal loops of type I with a transitional loop oriented between 12 and 3 o’clock), and thus likely belong to P. verruculata . Peronia verruculata is expected to be present in Djibouti (locality of some paralectotypes of S. gravieri ), but that still needs to be demonstrated with fresh material from the northwestern Indian Ocean (Somalia, Yemen, Oman) as well as from the Red Sea and the Persian Gulf.

Pieces of possibly up to three syntypes of Scaphis tonkinensis were located at the MNHN (MNHN-IM-2000-33700) but they are useless, poorly preserved, unidentifiable pieces of tissues. Determining the status of S. tonkinensis thus relies entirely on Labbé’s original description. Given that P. verruculata (unit #1) is the only species known in Vietnam, and that several characters provided by Labbé (1934a: 213) match its anatomy (muscular sac 12 mm long, intestinal loops of type I), S. tonkinensis is regarded as a junior synonym of P. verruculata (Tables 1 , 4 , 6 ).

No type material could be located for Scaphis lata . Determining the status of S. lata thus relies entirely on Labbé’s original description. Labbé’s original description to determine its status. Given that P. verruculata (unit #1) is the only species known in Vietnam, and that several characters provided by Labbé (1934a: 213) match its anatomy (muscular sac 8 mm long, intestinal loops of type I), S. lata is regarded as a junior synonym of P. verruculata . Labbé mentioned the presence of dorsal gills and so at least some of the syntypes of S. lata were Peronia slugs. The fact that he also described intestinal loops of type II (which is absent in Peronia ) means that he either made a mistake (all loops were of type I) or that some syntypes were not Peronia slugs.

Onchidium durum , originally described from the Red Sea, is regarded as a junior synonym of Peronia verruculata because, contrary to what was indicated in the original description, Onchidium durum is characterized by dorsal gills and intestinal loops of type I. It is presumed here that there is only one species of Peronia with intestinal loops of type I in the Red Sea. Labbé frequently confused types of intestinal loops; there are no well-documented cases of Peronia slugs with intestinal loops of type II.

Peronia persiae , originally described from the Persian Gulf, is regarded as a new junior subjective synonym of P. verruculata because its mitochondrial DNA sequences, represented by the GenBank "voucher LaFM7S" in our analyses, all cluster together within the unit #4 of P. verruculata (Fig. 2 ). An older name, P. gondwanae ( Labbé, 1934a), already refers to the unit #4 of P. verruculata (Tables 1 , 6 ). So, even in the hypothetical event that unit #4 would later need to be named as a distinct taxon (of subspecific or specific rank), P. persiae would still remain invalid because P. gondwanae would always take priority over it.

The description of P. persiae by Maniei et al. (2020a) is an example of the common but regrettable practice that consists in creating new species names without a comprehensive revision, which almost inevitably leads to increasing the number of unnecessary synonyms ( Dayrat 2005). Here are a few of the major methodological issues in the study by Maniei et al. (2020a). First, Maniei et al. (2020a) ignored the existence of many available Peronia species names, which is especially problematic in the case of names with type localities near the Persian Gulf (Table 1 ), such as Onchidium durum and Paraperonia jousseaumei with a type locality in the Red Sea, and Scaphis gravieri with a type locality in Mayotte. Second, Maniei et al. (2020a) decided to create a new name before the nomenclatural status of the other Peronia names was addressed. For instance, Maniei et al. (2020a: table S1) compared P. persiae with P. branchifera , P. ferruginea , P. gaimardi , and P. lata as if they were all valid names, but these names all refer to the unit #1 of P. verruculata (Tables 1 , 6 ). Third, Maniei et al. (2020a) only examined specimens of P. persiae from the Persian Gulf, which means that, for comparison, they relied exclusively on the literature which, as the present work shows, is plagued with taxonomic and anatomical errors. For instance, Maniei et al. (2020a: table S1) assumed that the intestinal loops of P. verruculata were of types I and II, but it is positively demonstrated here that the intestinal loops of P. verruculata are all of type I and that there are no loops of type II in Peronia . Fourth, apart from P. persiae , only P. verruculata and P. peronii are represented in the phylogenetic trees by Maniei et al. (2020a: figs 11, 12), exclusively based on sequences obtained from GenBank (many of which were misidentified). Most specimens in their phylogenetic trees are not even identified at the species level. Using DNA sequences to create a new species name while most species are not being included in phylogenetic analyses is highly problematic.

Maniei et al. (2020b) used the same mitochondrial COI sequences as in Maniei et al. (2020a) to compare metabolites between the Peronia slugs they called P. persiae and one Peronia individual from Bangka Island, near Sumatra, Indonesia. That specimen from Bangka Island, identified as Peronia sp. 7 by Maniei et al. (2020a) and as P. verruculata by Maniei et al. (2020b), belongs to the unit #1 of P. verruculata : its COI (MK993397) and 16S (MK993396) sequences cluster within unit #1. Note that the GenBank accession numbers for COI and 16S are switched in Maniei et al.'s (2020a) Table 2 .

Maniei et al. (2020b) summarized their rationale for creating the name P. persiae as follows: "The ABGD test revealed that specimens of P. persiae form a separate clade (clade 2). Thus, the specimens from two localities of the Persian Gulf (Iran), i.e. Bandar Lengeh and Lavan Island, were considered as a distinct new species." Mitochondrial loci alone are not sufficient evidence to delineate species: molecular delimitation analyses can over-split species based on population structure, particularly when these are based on a single locus ( Sukumaran and Knowles 2017). More importantly, very high intra-specific mitochondrial divergence has been repeatedly documented in several onchidiid genera (e.g. Goulding et al. 2018c; Dayrat et al. 2019a).

Maniei et al. (2020b) argue that research on metabolites requires sound taxonomic knowledge. That certainly is a commendable goal: indeed, any comparative work in any biological field should be based on correct taxonomy. Unfortunately, P. persiae is a junior synonym of both P. gondwanae and P. verruculata (Tables 1 , 6 ). So, the metabolites compared between " P. persiae " and " P. verruculata " merely are intra-specific differences (within P. verruculata ) due to the long geographic distance (between the Persian Gulf and Bangka Island) as well as, most likely, different diets: in fact, Maniei et al. (2020b) acknowledged in their introduction that numerous biotic and abiotic factors influence the chemical composition. To conclude anything about specific differences in metabolites among Peronia based on specimens from only two regions, one of which being represented by a single individual is, to say the least, premature. In order to demonstrate that distinct metabolites are found in distinct species, one needs to study actually distinct species, i.e., species that were reliably identified, and one also needs specimens of the same species from different habitats and from different locations. It is our hope that the present, comprehensive, taxonomic revision will help physiologists, biochemists, ecologists, etc., to identify Peronia slugs correctly.

Some comments are also needed regarding the original anatomical description of P. persiae by Maniei et al. (2020a). According to Maniei et al. (2020a: 510, fig. 6, table S1), the intestinal loops of P. persiae are of type II, but they are without doubt of type I: the transitional loop is oriented at ~ 5 o’clock, as in intestinal loops of type I (Fig. 1 ). The radular formulae provided by Maniei et al. (2020a: 509) fit well with what was observed here for the unit #4 of P. verruculata (Table 5 ), acknowledging individual variation: from 49 × 47.1.47 (in a live specimen 22 mm long) up to 71 × 87.1.87 (in a live specimen 65 mm long). The length of the spine of the accessory penial gland ("around 1.3 mm") reported by Maniei et al. (2020a: 513) is shorter than what was observed here (from 2.2 to 2.8 mm) but this trait is known to vary between individuals (Table 4 ). Maniei et al. (2020a: table S1) compared the shape of the tip of the spine of the accessory penial gland between species, but that trait varies greatly intra-specifically and is useless to distinguish species. Finally, Maniei et al. (2020a: 513, fig. 8B) reported some “fork-shaped” penial hooks, which were also observed here in the unit #4 of P. verruculata (Fig. 100C ).

Additional material (historical museum collections). A specimen from Tanimbar, Indonesia (WAM S26630) is identified as P. verruculata because of its accessory gland spine (1.5 mm long), its intestinal loops of type I (with a transitional loop at 3 o’clock), and its muscular sac (10 mm). Seven specimens from Zanzibar (MNHN-IM-2014-7989 and MNHN-IM-2014-7990) are also identified as P. verruculata because their internal anatomy is only compatible with that species (Table 4 ). Finally, specimens from the Persian Gulf (NHMD 635301) with intestinal loops of type I (with a transitional loop at 6 o’clock) demonstrate that there is more than one Peronia species in the Persian Gulf (Fig. 6 ). Indeed, based on our DNA sequences, P. madagascariensis (with intestinal loops of type V) is present in the Persian Gulf, and individuals with intestinal loops of type I must belong to a different species. Given that P. verruculata is known from Pakistan and western India (unit #4), eastern Africa (unit #5), and the Red Sea, it most likely lives in the Persian Gulf too. The fresh material recently described as P. persiae by Maniei et al. (2020a) confirms with molecular data the presence of the unit #4 of P. verruculata in the Persian Gulf (Fig. 2 ). In addition, several historical specimens preserved at various institutions were examined for the present study. They are discussed below in the secondary literature section because they were studied by previous authors.

Secondary literature. JE Gray (1850: 117) and Adams and Adams (1855: 235) did not mention Onchidium verruculatum in their list of Peronia species names. That might seem surprising because they transferred to Peronia all slugs with "radiating processes" ( Gray 1850: 117) or "arbusculiform tufts" (Adams and Adams 1855: 234) on the dorsal notum. And, clearly, Onchidium verruculatum refers to a species of slugs with such appendages. However, there is an explanation. Onchidium verruculatum was created by Cuvier (1830: 281) in reference to Savigny’s (1817: pl. 2, figs 3.1-3.8) illustrations (of slugs from the Red Sea) for which the figure captions by Audouin (1826: 18-20) used Cuvier’s (1804) older name Onchidium peronii , originally described from Mauritius. JE Gray (1850: 117) mentioned Savigny’s Onchidium peronii in his list of Peronia species names and ME Gray reproduced some of Savigny’s drawings: ME Gray’s (1850: pl. 183, figs 4, 4a, 5) illustrations are exact copies of Savigny’s (1817: pl. II, figs 3.1-3.3) illustrations. Note that Savigny (1817: pl. II, figs 3.1-3.3) illustrated two individuals which may or may not belong to the same species (see above, remarks on the type material of O. verruculatum ). Also, note that one of Savigny’s (1817: pl. 2, fig. 3.5) drawings beautifully illustrates dorsal gills, which JE Gray was certainly aware of. So, long story short, JE Gray (1850) knew the existence of Savigny’s (1817: pl. 2, figs 3.1-3.8) illustrations of slugs with dorsal gills from the Red Sea but decided to refer to them using Cuvier’s (1804) older name Onchidium peronii (from Mauritius) and ignore Cuvier’s (1830) newer name O. verruculatum (specifically created for those slugs from the Red Sea). Similarly, Adams and Adams (1855: 235) mentioned P. peronii with a reference to Savigny’s (1817) plate, not to Cuvier’s (1804) original description of P. peronii , which means that, exactly like JE Gray (1850), Adams and Adams (1855: 235) decided to ignore Cuvier’s newer name Onchidium verruculatum created for the slugs on Savigny’s plate.

Keferstein (1865b) described as Peronia verruculata three slugs from Nagasaki, Japan. Keferstein’s (1865b: pl. VI, fig. 16) drawing of the internal anatomy unmistakably illustrates intestinal loops of type V, which means that he examined P. setoensis instead of P. verruculata (see remarks on P. setoensis ). It is unclear whether Keferstein’s (1865a: pl. CII, figs 20*, 20**, pl. CV, figs 1, 2) drawings illustrate the same Nagasaki individual as the one with intestinal loops of type V ( Keferstein 1865b: pl. VI, fig. 16). It cannot be excluded that Keferstein examined several of the species found in Japan (Fig. 6 ). Keferstein (1865a: pl. CIV, figs 9-12) also reproduced four of Savigny’s (1817: pl. 2, figs 3.2, 3.3, 3.5, 3.7) original drawings used as a reference by Cuvier for the name Onchidium verruculatum . And note, again, that the two individuals illustrated by Savigny may or may not both belong to O. verruculatum : one specimen belongs to P. verruculata but the other may belong to P. madagascariensis (see above, remarks on the type material of O. verruculatum ). At any rate, to our knowledge, it is in Keferstein’s (1865a, b) work that Onchidium verruculatum was first transferred to Peronia .

Both H. Nevill (1870: 304-305) and G. Nevill (1878: 1) mentioned the presence of Onchidium verruculatum in Ceylon. It most likely refers to P. verruculata , although there possibly is more than one mitochondrial unit in southern India.

Mörch (1872a: 28; 1872b: 325) mentioned Peronia verruculata (as spelling mistake vermiculata in 1872b) from Pulo Milu [Pulo Milo, Little Nicobar] and Nancouri [Nancowry, Nicobar Islands], where he says it is common. Those specimens, re-examined for the present study (NHMD 613753), are a record of P. peronii (see remarks on P. peronii ).

Specimens collected during the Galathea Expedition from a bay in Sambelong, Great Nicobar, were examined and the largest individual (35/28 mm) was dissected (NHMD 635300). Those specimens are important historically because they were mentioned by several authors (see below). Given their size (35/28 to 20/15 mm), their digestive system (type I with a transitional loop oriented at 6 o’clock, in the largest individual), and the size of their accessory gland spine (1 mm in the largest individual), those specimens belong to P. verruculata , but could potentially belong to more than one mitochondrial unit (Table 4 ). Mörch (1872a: 28; 1872b: 325) first mentioned them as Peronia mauritiana . Semper (1880: 255) identified them as O. verruculatum . Bergh (1884a) described one of them in detail (see below). Hoffmann (1928: 44, 73) also listed them in his material examined for O. verruculatum .

Schmeltz (1874: 96) listed Peronia verruculata from Samoa in a catalog of the Museum Godeffroy. This possibly is a record of P. peronii , although P. platei could also live there (Fig. 6 ).

Ihering (1877: 230-237, pl. IV, fig. 3) described the nervous system of Peronia verruculata but did not provide any information on the specimens he examined. It is impossible to determine what Peronia species he actually studied.

Fischer and Crosse (1878: 689-690, pl. XXXI, figs 13-15) briefly described the radula of specimens they identified as Onchidium (Peronia) verruculatum from New Caledonia. There are three Peronia species in New Caledonia, and it is not possible to determine what species they examined.

Semper (1880: 255-257, pl. 22, figs 3, 4; 1882: pl. 21, fig. 1) re-described O. verruculatum based on specimens from a variety of localities (Red Sea, East Coast of Africa, Nicobar, Ambon, eastern Australia, Philippines). His written description mostly focuses on traits that are not informative for species identification (e.g., number of dorsal papillae, number of dorsal eyes, radular teeth). Some of Semper’s records of P. verruculata most likely are correct, given the geographic origin of the material (Fig. 6 ): Ambon, Philippines, and Cape York (Queensland, Australia). Some other material could be a mix of more than one species: P. madagascariensis and P. verruculata in the Red Sea and eastern Africa; P. verruculata and P. sydneyensis in MacKay, Queensland. Semper’s material from Brisbane (27°S) most likely was part of P. sydneyensis (Fig. 6 ). Finally, Semper’s specimen from Nicobar was part of some material collected during the Galathea Expedition and first reported by Mörch (1872a: 28; 1872b: 325) as Peronia mauritiana (NHMD 635300). Those specimens, re-examined for the present study, belong to P. verruculata (see above).

Bergh (1884a: 148-151, pl. VII, figs 7-12, pl. VIII, fig. 14) described in detail the anatomy of an individual of O. verruculatum from Nicobar. The animal size (33/23 mm) and the size of the accessory penial gland spine (1.76 mm) match well the anatomy of P. verruculata (unit #1). This specimen was part of a group of specimens collected during the Galathea Expedition in Sambelong, Great Nicobar, which were examined for the present study (NHMD 635300). Their size (35/28 to 20/15 mm), their digestive system (type I with a transitional loop oriented at 6 o’clock, in the largest individual), and the length of their accessory gland spine (1 mm in the largest individual) are also compatible with P. verruculata . However, those specimens could potentially belong to more than one mitochondrial unit (Fig. 6 ).

Plate’s (1893: 168-170, pl. 7, figs 11, 12, 15, pl. 8, figs 26, 33, pl. 9, figs 36-40, pl. 10, figs 50a, 55, pl. 11, fig. 56, pl. 12, figs 83, 88, 90, 98) re-description of Onchidium verruculatum was based on specimens from Ambon, Ceylon, and Nicobar. Given the size (at most 50 mm long), it seems likely that Plate examined P. verruculata . However, without precise measurements of the spine of the accessory penial gland, it is not possible to ascertain that Plate examined P. verruculata (e.g., P. peronii is also present in Nicobar). According to Plate, the only anatomical difference between O. verruculatum and O. savignyi Semper, 1880, is that dorsal gills are "much longer and tubular" in O. savignyi , which is a weak character, to say the least. At any rate, Peronia savignyi (Semper, 1880) is deemed to be identical to Peronia savignii Récluz, 1869 ( ICZN 1999: Article 58) and, as junior secondary homonym, is subjectively invalid ( ICZN 1999: Article 57.3) (see remarks on synonymies above). Plate (1893) did not compare O. verruculatum to any other species.

Von Martens (1897: 126) mentioned Onchidium verruculatum from both Ambon and Timor with no description. Our molecular data indicate that Peronia verruculata does live in Ambon and Timor. However, Peronia peronii also lives in Timor and likely lives in Ambon too.

Farran (1905: 358-359, pl. VI, figs 13-22) described a Peronia slug he identified as Onchidium verruculatum from the Gulf of Mannar based on one preserved specimen. Given the specimen size (31/34 mm) and the length of the spine of the penial accessory gland (2.8 mm), it is likely a record of P. verruculata , but it is unclear whether it is the unit #2 (known from the Andaman Islands) or unit #4 (known from Mumbai, western India). It could also be a record of a small, immature individual of P. peronii (which has not been recorded from southern India but could possibly be found there). Our present study does not include any specimen from Sri Lanka or the Gulf of Mannar.

Onchidium verruculatum is one of the eight onchidiid species mentioned by Hedley (1909: 369) from Queensland, Australia, without any reference to any material. It is impossible to know what species Hedley refers to. Our data show that there are two Peronia species in Queensland which overlap geographically (Fig. 6 ).

The references listed by Bretnall (1919: 310) for Onchidium verruculatum are all commented on above already. Let us say a few words about the specimens he examined himself. Bretnall’s (1919: 310) records of O. verruculatum from Broken Bay, New South Wales (33°30'S) are likely records of Peronia sydneyensis , the only Peronia species known in New South Wales (Fig. 6 ). Bretnall’s (1919: 310) records of O. verruculatum from Port Curtis, Queensland (ca. 23°30'S) could be records of P. sydneyensis but they could also include P. verruculata because the known southernmost locality of the mitochondrial unit #1 of P. verruculata is at ca. 21S (see remarks on P. sydneyensis ).

The record of Onchidium verruculatum from Katsepy ( Catsèpe), northwestern Madagascar, by Odhner (1919: 23) is within the geographical range of both P. verruculata (unit #5) and P. madagascariensis (Fig. 6 ). The voucher specimen, re-examined here (SMNH 180724), clearly belongs to P. verruculata because of its intestinal loops of type I (with a transitional loop at 6 o’clock).

Hoffmann (1928: 72) listed many references for O. verruculatum , all of which (but one) are commented upon elsewhere already: comments on the references for Onchidium peronii , O. punctatum , and Peronia mauritiana can be found in our remarks on P. peronii ; comments on the references for Onchidium ferrugineum and O. elberti can be found above, in our remarks on synonymies; Peronia alderi is regarded as a nomen dubium and is commented on in the general discussion. Mörch’s (1872a: 28; 1872b: 326) record of Peronia (Onchidiella) marmorata from Nicobar Islands, which Hoffmann (1928: 72) included in his list of correct references for O. verruculatum , is commented on here: it is not possible to know to what species Mörch refers; Godwin-Austen (1895: 443) listed Mörch’s record as Onchidium (Onchidiella) marmorata in a faunistic inventory of Nicobar and Andaman, without clarifying to what species that name was referring. At any rate, Lesson’s (1831b) Onchidium marmoratum belongs to Marmaronchis ( Dayrat et al. 2018).

More importantly, Hoffmann (1928: 44) examined specimens from the collections in Stockholm and Copenhagen which he identified as O. verruculatum . Most of those specimens could be re-examined for the present study and are commented on here. Several specimens are confirmed here to belong to P. verruculata based on diagnostic anatomical traits (Table 4 ): the material from Karachi (SMNH 180721) belongs to the unit #4 of P. verruculata ; the material from Hong Kong (SMNH 180707) and Queensland (SMNH 180712, 180713, 180714) belongs to the widespread unit #1; the material from Singapore (SMNH 180716) and the Java Sea (SMNH 180719, 180720, 180722) could belong to any of the three units (#1, #2, #3) present in the region. However, several specimens listed by Hoffmann (1928: 44, 72) clearly do not belong to P. verruculata (see remarks on each corresponding species): the specimen from Port Natal, South Africa (SMNH 180711) belongs to P. madagascariensis ; the specimen from Sagami Bay, Japan (SMNH 180725) belongs to P. setoensis ; and the specimen from Port Darwin, Northern Australia (SMNH 180715) belongs to P. willani .

The Red Sea specimens from the Copenhagen collections listed as "Savigny leg., Mus. Marsil" belong to P. verruculata because of their intestinal loops of type I (NHMD 90791). The label in the jar says that they were obtained by the Copenhagen Museum in 1860 (journal entry) from Savigny and the museum of Marseille (erroneously spelled “Marsielle”). Given that the type material of O. verruculatum was originally illustrated by Savigny (1817), it is worth making it clear here that those specimens are not the type material of O. verruculatum (Hoffmann did not say they were). The type material of O. verruculatum is in Paris (MNHN-IM-2000-22941).

The other specimens mentioned by Hoffmann (1928: 44, 73) could not be re-examined for the present study: the specimens from the Red Sea could potentially belong to P. verruculata or P. madagascariensis ; the specimens from Tharangambadi (Tranquebar), southeastern India, most likely belong to P. verruculata ; the specimens from New Caledonia could potentially belong to any of the three species present there; the specimens from Hawaii clearly belong to P. platei .

All the references mentioned by Labbé (1934a: 192-193) for Peronia verruculata are already commented on above. Labbé (1934a: 193) blindly accepted the distribution provided by Hoffmann (1928: 44, 73), which was not accurate because, for instance, P. verruculata is not present in Hawaii (see above). Labbé (1934a: 193) mentioned intestinal loops of type II in one individual from the Red Sea, even though he did not list any material examined from the Red Sea. At any rate, those intestinal loops were most likely of type I as aforementioned Labbé often made that kind of mistake. For instance, Labbé (1934a: 196) described as P. anomala a species with supposedly anomalous intestinal loops of type II, but the type material, re-examined here, clearly is characterized by loops of type I (Fig. 86B ). The specimens examined by Labbé from the Philippines likely belong to P. verruculata , but the individuals from New Caledonia or New Guinea could belong to several Peronia species. Finally, so far, only P. peronii and P. griffithsi are positively known from Mauritius and his record of P. verruculata there (as Ile de France) must not be taken for granted.

The record of Onchidium (Peronia) verruculatum from Natal, South Africa ( Connolly 1939: 454) likely is a record of P. madagascariensis , the only Peronia species so far known from South Africa. However, P. verruculata (unit #5) could also be found in northeastern South Africa because its southernmost known locality is in Maputo (ca. 26°S), very close to South Africa.

Allan and Bell (1947: 152) and Allan (1950: 368) reported onchidiid slugs living in dead coral which they identified as Onchidium verruculatum from Moreton Bay, Brisbane, Queensland, Australia. Given its latitude (ca. 27°S), Brisbane is clearly in the range of P. sydneyensis and possibly of P. verruculata (unit #1) as well. Indeed, it is still unclear how far south P. verruculata is distributed in southeastern Australia, although we did not find it in Sydney, ca. 33S (see remarks on P. sydneyensis ).

For the record of O. verruculatum from New South Wales by Dakin (1947: 144), see remarks on P. sydneyensis .

Awati and Karandikar (1948) published a detailed anatomical study of a species they identified as Onchidium verruculatum based on material from the western coast of India. They mention four localities: Vengurla (ca. 15°50'S), Malvan (ca. 16°06'S), Mumbai (ca. 19°S), and Kathiawar (ca. 21°S). The illustration of the intestinal loops provided by Awati and Karandikar (1948: fig. 6) leaves no doubt about the fact that they examined individuals of P. madagascariensis , a species with intestinal loops of type V distributed from South Africa all the way to (at least) Mumbai. Whether a type V was observed by the authors in all the specimens, including those from the southernmost localities (Vengurla and Malvan), is unclear. The presence of intestinal loops of type V in all the specimens examined by Awati and Karandikar (1948) would mean that P. madagascariensis is found much farther south than Mumbai. If the authors did not notice that some intestinal loops were of type I, then they described two species under the name Onchidium verruculatum : P. madagascariensis and P. verruculata (Fig. 6 ).

Baba (1958: 144) reported that some individuals of Onchidium verruculatum from Tokara Islands (ca. 30°N), just south of Kyushu, were very large (up to 120 mm long), suggesting that they were P. peronii instead (see remarks on P. peronii ). The smaller specimens, however, could be P. verruculata (unit #1) and possibly P. setoensis (see remarks on P. setoensis ). The two species which Baba (1958: 21) seems to distinguish (as Onchidium and Onchidium verruculatum ) from Misaki (ca. 34°N), near Osaka, could be P. verruculata (unit #1) and P. setoensis , which, based on our DNA sequences, are sympatric near the Seto Marine Laboratory, which is close to Osaka (Fig. 6 ).

Solem (1959: 39) recorded O. verruculatum from Vanuatu (Esperitu Santo) which hosts at least two species: P. verruculata (unit #1) and P. peronii (Fig. 6 ). The references that he mentioned ( Bretnall 1919; Hoffmann 1928; Awati and Karandikar 1948) are already commented on above. His proposed distribution ("Esperitu Santo, Africa to Japan, New Guinea, Australia and New Caledonia. Also common in Hawaii, but not known from Polynesia") is inaccurate (Fig. 6 ). For instance, the only Peronia species in Hawaii is P. platei (for comments on Solem’s comparison between O. peronii and O. verruculatum , see remarks on P. peronii ).

Menon et al. (1961: 493, pl. 10, fig. 84) mentioned Onchidium verruculatum in the Gulf of Kutch, northwestern India, which is within the distribution range of both P. madagascariensis and P. verruculata (Fig. 6 ). Our data suggest that P. verruculata (mitochondrial unit #4) is found from Pakistan (north of the Gulf of Kutch) to Mumbai (south of the Gulf of Khambhat). Also, a paralectotype of P. gondwanae from Mumbai (MNHN-IM-2000-33682) with intestinal loops of type V suggests that P. madagascariensis lives south of the Gulf of Kutch and Gulf of Khambhat.

Marcus and Marcus (1970: 213) recorded P. verruculata from Madagascar based on one specimen (45/20 mm) for which they reported intestinal loops of type II. Most likely, they confused types of intestinal loops (there are no documented intestinal loops of type II in Peronia slugs). The specimen they examined likely belongs to P. verruculata (unit #5), characterized by intestinal loops of type I, but it could also belong to P. madagascariensis , which is characterized by intestinal loops of type V. Both species were recorded in Madagascar and both are characterized by a retractor muscle inserting at the end of the visceral cavity, a trait reported by Marcus and Marcus (1970: 213).

For the record of O. verruculatum from the central coast of New South Wales by Smith and Kershaw (1979: 92), see remarks on P. sydneyensis .

Gopinadha Pillai and Appukuttan (1980: 34) listed Onchidium verruculatum in the Gulf of Mannar, with no description or material. It likely refers to P. verruculata .

Hutchings and Recher (1982: 119) listed Onchidium verruculatum from Northern Territory, Queensland, and New South Wales, Australia. Based on our data, O. verruculatum (unit #1) is only present in Queensland, but it cannot be excluded that it also is present in northern New South Wales (see remarks on P. sydneyensis ). Northern Territory and New South Wales host other species than P. verruculata (Fig. 6 ).

Britton (1984: 183-184, fig. 2) described Peronia verruculata from Hong Kong. Some of the specimens he examined clearly are Peronia slugs because he mentioned dorsal gills, and they most likely belong to Peronia verruculata (unit #1), the only species known from the coast of China (Fig. 6 ). However, his specimen with intestinal loops of type II (NHMUK 1982284) was misidentified because there are no intestinal loops of type II in Peronia .

Katagiri and Katagiri (2007) distinguished two species (both as Onchidium verruculatum ) in the waters of the Boso Peninsula (ca. 35N, near Sagami Bay, Honshu) based on external appearance and development. Most likely, those two species correspond to P. verruculata (unit #1) and P. setoensis , which are the only two Peronia species found north of 30N (Fig. 6 ; see remarks on P. setoensis ).

The name Peronia verruculata mentioned in ecological studies in Japan ( Nakaoka et al. 2006; Wardiatno et al. 2015) can potentially refer to any of the four Peronia species found in Japan (Fig. 6 ). The name P. verruculata mentioned from Mumbai and the Gulf of Khambhat, northwestern India ( Mandal and Harkantra 2013; Solanki et al. 2017), could refer to both P. verruculata (unit #4) and P. madagascariensis (Fig. 6 ). The name P. verruculata mentioned from the coast of mainland China ( Sun et al. 2014, 2016; Liu et al. 2015; Xu et al. 2018) refers to the mitochondrial unit #1 of P. verruculata (Fig. 6 ). The name P. verruculata mentioned from the Andaman Islands ( Santhosh Kumar et al. 2016) could refer to more than one mitochondrial unit of P. verruculata (Fig. 6 ). The name Peronia sp. mentioned from Vietnam ( Zvonareva and Kantor 2016: 432, fig. 9D) most likely refers to the mitochondrial unit #1 of P. verruculata (Fig. 6 ).

Chang et al. (2018) reported two Peronia least-inclusive units in Singapore based on COI sequences, which correspond to our mitochondrial units #1 (their " Peronia sp. 2 clade") and #3 (their "Singapore clade"): two of their COI sequences were included in our mitochondrial analyses (Table 2 and Fig. 2 ). Chang et al. (2018) also reported some anatomical differences between those two units, mostly because they only examined individuals from Singapore. The variation in the number of dorsal eyes per dorsal papilla is not different between both units: for instance, up to eight dorsal eyes per papilla are present in our individual [2987] from Lombok. The diameter measurements of the conical base of the spine of the accessory penial gland overlap: they reported 113-181 μm in unit #1 and 187-267 μm in unit #3, but ranges of 100-270 μm in unit #1 and 200-270 μm in unit #3 were observed here (Table 4 ). Finally, the ranges in diameter at the tip of the spine also overlap between both units: 35-50 μm in unit #1 and 40-80 μm in unit #3 (Table 4 ).

Two specimens from Mozambique ([730] NHMUK 20080190, and [733] NHMUK 20060257), tentatively identified as Peronia sp. 4 and sp. 5 respectively by Dayrat et al. (2011: 428), belong to the unit #5 of P. verruculata (Fig. 2 ). The specimens [731] (NHMUK 20050628) from Sulawesi, Indonesia, and [712] (UF 368518) from Cebu, Philippines, referred to as Peronia sp. 6 and Scaphis sp. respectively by Dayrat et al. (2011), belong to the unit #1 of P. verruculata (Fig. 2 ).

A few COI sequences available in GenBank are not included in our analyses because they do not add any information regarding the species distribution. Ran et al. (2020) published four COI Peronia sequences from Hainan, China (MN389204 to MN389207), which all cluster within P. verruculata unit #1. Two unpublished sequences (MN690327 and MN690328) from Singapore (uploaded in November 2019 by Ip and colleagues) cluster within P. verruculata units #1 and #3. A COI sequence (MK993397) from Bangka, Indonesia, identified as Peronia sp. 7 by Maniei et al. (2020a) and as P. verruculata by Maniei et al. (2020b), cluster within P. verruculata unit #1. Note that the GenBank accession numbers for COI and 16S of that Bangka Island individual are switched in Maniei et al.'s (2020a) Table 2 . Finally, a sequence (EF489391) from Queensland, Australia, identified as Onchidium verrucosum (a spelling mistake for O. verruculatum ) by Klussmann-Kolb et al. (2008), cluster within P. verruculata unit #1.

Figures

Figure 1. Intestinal types found in Peronia species. A clockwise intestinal loop is colored in blue, a counterclockwise intestinal loop is colored in yellow, and a transitional loop between them is colored in green. The big red arrow indicates the orientation of the transitional loop (A-F) or counterclockwise loop (G-I), and the small black arrows indicates the direction of the intestinal transport A type I, with a transitional loop oriented at 3 o'clock, P. sydneyensis, Australia, New South Wales, [1517] (AM C. 468915.001) B type I, with a transitional loop oriented at 6 o'clock, P. verruculata, lectotype of P. anomala, Red Sea (MNHN-IM- 2000 - 33678) C type I, with a transitional loop oriented between 4 and 5 o'clock, P. verruculata, lectotype, Red Sea (MNHN-IM- 2000 - 22941) D type I, with a transitional loop oriented at 3 o'clock, P. peronii, paralectotype of Onchidium peronii, Timor (MNHN-IM- 2000 - 22938) E type I, with a transitional loop oriented at 1 o'clock, P. peronii, lectotype of Paraperonia fidjiensis, Fiji (MNHN-IM- 2000 - 33692) F type I, with a transitional loop oriented between 1 and 2 o'clock, P. okinawensis, holotype, Japan, Okinawa, [696 - 4 H] (UF 352288) G type V, with a counterclockwise loop oriented between 10 and 11 o'clock, P. madagascariensis, Madagascar, [5501] (MNHN-IM- 2009 - 16392) H type V, with a counterclockwise loop oriented at 10 o'clock, P. platei, lectotype, French Polynesia (SMNH-Type- 7537) I type V, with a counterclockwise loop oriented at 11 o'clock, P. griffithsi, holotype, Mauritius, [3157 H] (MNHN-IM- 2000 - 35265). Scale bars: 2 mm (A, B), 5 mm (C-G), 3 mm (H, I).

Figure 2. Phylogenetic relationships between Peronia species based on concatenated mitochondrial COI and 16 S DNA sequences. Numbers by the branches are the bootstrap values (maximum likelihood analysis) and the posterior probabilities (Bayesian analysis). Only the values> 50 % (ML) and> 0.9 (Bayesian) are indicated. Numbers for each individual correspond to unique identifiers for DNA extraction. Information on specimens can be found in the lists of material examined and in Table 2. The color used for each species or mitochondrial unit is the same as the color used in Figs 3 - 6.

Figure 6. Geographical distribution of the Peronia species A distribution of all Peronia species except for P. peronii B distribution of P. peronii. The colors are the same as those used in Figs 2 - 5. Colored areas correspond to hypothetical geographical ranges based on confirmed records only. Distinct colors are used for each unit of P. verruculata. The distribution of P. verruculata in the Indo-West Pacific is actually continuous. However, because it is unclear which units are present in regions from where we have no fresh material of P. verruculata (red areas), no unit of P. verruculata is shown there. For P. peronii, black dots correspond to material identified based on anatomical characters and blue dots correspond to material with DNA sequences. Details on species distribution can be found in each species description.

Figure 9. Digestive system, dorsal view, Peronia peronii, type specimens. The arrow indicates the orientation of the transitional loop A paralectotype, Onchidium peronii, Timor (MNHN-IM- 2000 - 22938) B lectotype, Onchidium tonganum, Tonga (MNHN-IM- 2000 - 22937) C lectotype, Onchidium punctatum, Indonesia, West Papua (MNHN-IM- 2000 - 22966) D possible paralectotype, Paraperonia gondwanae, Mauritius (MNHN-IM- 2000 - 33686) E lectotype, Paraperonia fidjiensis, Fiji (MNHN-IM- 2000 - 33692). Scale bars: 5 mm (A, D), 10 mm (B, C, E). Abbreviations: ddg dorsal digestive gland, i intestine, pdg posterior digestive gland, st stomach.

Figure 21. Peronia madagascariensis A-D digestive system, dorsal view, with intestinal loops of type V E posterior, hermaphroditic (female) reproductive system A holotype, Paraperonia madagascariensis, Madagascar (MNHN-IM- 2000 - 33680) B paralectotype, Paraperonia gondwanae, Mumbai, western India (MNHN-IM- 2000 - 33682) C paralectotype, Paraperonia gondwanae, Red Sea (MNHN-IM- 2000 - 33683) D Madagascar, [5501] (MNHN-IM- 2009 - 16392) E same as D. Scale bars: 5 mm (A-D), 2 mm (E). Abbreviations: dd deferent duct, ddg dorsal digestive gland, fgm female gland mass, hg hermaphroditic gland, i intestine, ov oviduct, pdg posterior digestive gland, rs receptaculum seminis, sp spermatheca, st stomach.

Figure 65. Habitats, Peronia verruculata (unit 1) A Singapore B-H Indonesia A Mangrove forest with rich litter, lobster mounds, dead logs, with sand area near the creek (st 5) B Sumatra, coral rubble on beach exposed to estuary (st 78) C Sulawesi, old Sonneratia and Avicennia mangrove (st 84) D Ambon, narrow band of old Avicennia trees on sandy mud, old logs on ground (st 132) E Seram, mud next to a mangrove (st 135) F Lombok, old Avicennia forest with coral rubble (st 149) G Halmahera, rocky shore near a beach (st 217) H Timor, sandy part of mangrove with Sonneratia and Avicennia trees (st 250).

Figure 66. Habitats, Peronia verruculata (unit 1) A Australia, Queensland, rocky shore nearby a small and dense Rhizophora mangrove patch (st 113) B New Caledonia, coastal rocky mangrove (st KM 537) C Papua New Guinea, New Ireland, mixed hard platform and seagrass bed at outlet of rivulet (st KM 05) D Papua New Guinea, Madang, limestone rocky intertidal (st PM 12) E Vietnam, mangrove patch with many big flat rocks outside (st 236) F Vietnam, coral rubble near small Rhizophora sandy and muddy mangrove (st 238) G Philippines, Bohol, coral rubble with sand and algae, near Sonneratia (st 202) H sandy, open Avicennia forest, right by the shore (st 181).

Figure 67. Habitats, Peronia verruculata (unit 2) A India, South Andaman, rocky shore with a patch of Rhizophora, sand and coral rubble but no mud (st 53) B India, South Andaman, rocky shore only, no mangrove (st 54) C India, South Andaman, sandy beach with coral rubble (st 53) D Indonesia, Sumatra, coral rubble on beach exposed to estuary (st 78) E Indonesia, Sumatra, beach with a few rocks (st 82).

Figure 68. Habitats, Peronia verruculata (unit 3) A Singapore, rocky shore covered by oyster flats (st 2) B slugs on the rocks, same as A (st 2) C Singapore, rocks of artificial breakwaters (st 3) D Peninsular Malaysia, Langkawi, large boulders on sand beach (st 25).

Figure 69. Habitats, Peronia verruculata A unit 4 B, C unit 5 A India, Mumbai, solid rock area, some crevices (st 44) B Madagascar, sandy mangrove of Bruguiera, on sandy mud in between rocks (st 162) C Madagascar, rocky platform near Avicennia and Rhizophora mangrove (st 158).

Figure 70. Live animals, dorsal view, Peronia verruculata (unit 1), Indonesia A 40 mm long [1747], Sumatra (UMIZ 00172) B 40 mm long [2987], Lombok (UMIZ 00168) C 20 mm long [3080], Bali (UMIZ 00164) D 20 mm long [3115], Bali (UMIZ 00165) E 45 mm long [2856], Ambon (UMIZ 00163) F 40 mm long [2729], Ambon (UMIZ 00162) G 50 mm long [2868], Seram (UMIZ 00169) H 55 mm long [3441], Seram (UMIZ 00169).

Figure 71. Live animals, dorsal view, Peronia verruculata (unit 1) A-E Indonesia F-H Vietnam A 35 mm long [5130], Halmahera (UMIZ 00167) B 40 mm long [5120], Halmahera (UMIZ 00167) C 50 mm long [5124], Halmahera (UMIZ 00167) D 35 mm long [5927], Timor (UMIZ 00175) E 45 mm long [5904], Timor (UMIZ 00174) F 60 mm long [5620] (ITBZC IM 00021) G 40 mm long [5621] (ITBZC IM 00021) H 17 mm long [5639] (ITBZC IM 00023).

Figure 72. Live animals, dorsal view, Peronia verruculata (unit 1) A-C New Caledonia D-G Philippines A 50 mm long [6202] (MNHN-IM- 2019 - 1591) B 73 mm long [6212] (MNHN-IM- 2019 - 1592) C 43 mm long [6214] (MNHN-IM- 2019 - 1593) D 35 mm long [3437], Bohol (PNM 041276) E 50 mm long [3160], Luzon (PNM 041277) F 30 mm long [3433], Bohol (PNM 041276) G 40 mm long [3161], Luzon (PNM 041277).

Figure 73. Live animals, ventral view, Peronia verruculata (unit 1) A-F Indonesia G-I Philippines, Bohol J Vietnam K, L New Caledonia A 45 mm long [2127], Sulawesi (UMIZ 00170) B 60 mm long [2162], Sulawesi (UMIZ 00171) C 50 mm long [5124], Halmahera (UMIZ 00167) D 40 mm long [5120], Halmahera (UMIZ 00167) E 50 mm long [2868], Seram (UMIZ 00169) F 45 mm long [5904], Timor (UMIZ 00174) G 40 mm long [3379] (PNM 041274) H 35 mm long [3380] (PNM 041274) I 30 mm long [3433] (PNM 041276) J 60 mm long [5620] (ITBZC IM 00021) K 50 mm long [6202] (MNHN-IM- 2019 - 1591) L 73 mm long [6212] (MNHN-IM- 2019 - 1592).

Figure 74. Live animals, Peronia verruculata (unit 2) A dorsal view, 50 mm long [1746], Indonesia, Sumatra (UMIZ 00178) B dorsal notum, detail, same as A; C dorsal view, 25 mm long [1741], Indonesia, Sumatra (UMIZ 00179) D dorsal view, 45 mm long [1795], Indonesia, Sumatra (UMIZ 00180) E dorsal view, 30 mm long [1080], India, South Andaman (BNHS 121) F dorsal view, 15 mm long [1079], India, South Andaman (BNHS 120) G Ventral view, same as A; H ventral view, same as D; I ventral view, same as C.

Figure 75. Live animals, Peronia verruculata (unit 3) A dorsal view, 35 mm long [974] at the bottom, 27 mm long [975] at the top, 35 mm long [976] on the left, 27 mm long [977] on the right, Peninsular Malaysia, Langkawi (USMMC 00051 & 00064) B dorsal notum, detail [974], Peninsular Malaysia, Langkawi (USMMC 00064) C ventral view, 35 mm long [976], Peninsular Malaysia, Langkawi (USMMC 00051) D dorsal view, 25 mm long [990], Singapore (ZRC. MOL. 10496) E ventral view, same as D.

Figure 76. Live animals, Peronia verruculata (unit 4), India, Mumbai A dorsal view, 55 mm long [1141] (BNHS 22) B dorsal view, 60 mm long [1143] (BNHS 24) C dorsal view, 60 mm long [1144] (BNHS 23) D ventral view, same as C.

Figure 77. Live animals, Peronia verruculata (unit 5), Madagascar A dorsal view, 30 mm long [3142] (MNHN-IM- 2019 - 1610) B dorsal view, 50 mm long [3143] (MNHN-IM- 2019 - 1611) C dorsal view, 30 mm long [3146] (MNHN-IM- 2019 - 1611) D dorsal view, 30 mm long [3149] (MNHN-IM- 2019 - 1611) E dorsal view, 13 mm long [3598] (MNHN-IM- 2019 - 1610) F dorsal view, 30 mm long [3600] (MNHN-IM- 2019 - 1611) G ventral view, same as A; H ventral view, same as C; I ventral view, same as D.

Figure 78. External morphology and nervous system, Peronia verruculata (unit 1), Indonesia, Sulawesi [2127] (UMIZ 00170) A anterior, ventral view B posterior, ventral view, the dotted line shows where the foot normally expands (it was partly cut to illustrate the anus, the peripodial groove, and the female pore) C dorsal gills and papillae D nervous system, dorsal view. Scale bars: 5 mm (A, B), 2 mm (C), 1 mm (D). Abbreviations: a anus, f foot, fo female opening, h hyponotum, lcg left cerebral ganglion, lpg left pedal glanglion, lplg left pleural ganglion, mo male opening, ol oral lobe, ot ocular tentacle, pn pneumostome, ppg peripodial groove, rcg right cerebral ganglion, rpg right pedal glanglion, rplg right pleural ganglion, vg visceral ganglion.

Figure 79. Digestive system, Peronia verruculata (unit 1), Indonesia, Sulawesi [2127] (UMIZ 00170) A dorsal view, the arrow indicates the orientation of the transitional loop B ventral view C stomach, dorsal view D stomach, ventral view. Scale bars: 5 mm (A, B), 4 mm (C, D). Abbreviations: ddg dorsal digestive gland, i intestine, ldg lateral digestive gland, oddg opening of the dorsal lobe of the digestive gland, oldg opening of the lateral lobe of the digestive gland, opdg opening of the posterior lobe of the digestive gland, pdg posterior digestive gland, st stomach, st 1 first stomach chamber, st 2 second stomach chamber, st 3 third stomach chamber, st 4 fourth stomach chamber.

Figure 80. Digestive system, dorsal view, Peronia verruculata (unit 1), type specimens. The arrow indicates the orientation of the transitional loop A lectotype, Onchidium ferrugineum (MNHN-IM- 2000 - 22951) B holotype, Onchidium elberti (SMF 45248) C holotype, Scaphis astridae (RBINS I. G. 9223 / MT. 3822) D holotype, Scaphis carbonaria (MNHN-IM- 2000 - 33708) E lectotype, Peronia gaimardi (MNHN-IM- 2000 - 33705) F lectotype, Scaphis viridis (MNHN-IM- 2000 - 22964). Scale bars: 4 mm (A-C), 5 mm (D-F). Abbreviations: ddg dorsal digestive gland, i intestine, pdg posterior digestive gland, st stomach.

Figure 81. Digestive system, dorsal view, Peronia verruculata (unit 1). The arrow indicates the orientation of the transitional loop A Palau [698] (UF 253871) B Singapore [991] (ZRC. MOL. 10497) C Australia, Queensland [2622] (MTQ) D Philippines, Bohol [3380] (PNM 041274) E Philippines, Bohol [3433] (PNM 041276) F Japan, Honshu [3751] (NSMT-Mo 78988). Scale bars: 5 mm (A, D-F), 3 mm (B, C). Abbreviations: ddg dorsal digestive gland, i intestine, pdg posterior digestive gland, st stomach.

Figure 82. Peronia verruculata (unit 2), Indonesia, Sumatra, [1746] (UMIZ 00178) A digestive system, dorsal view, the arrow indicates the orientation of the transitional loop B posterior, hermaphroditic (female) reproductive system C anterior, male, copulatory apparatus. Scale bars: 5 mm (A, C), 4 mm (B). Abbreviations: ag accessory penial gland, dd deferent duct, ddg dorsal digestive gland, fgm female gland mass, hg hermaphroditic gland, i intestine, ms muscular sac, ov oviduct, pdg posterior digestive gland, ps penial sheath, rm retractor muscle, rs receptaculum seminis, sp spermatheca, st stomach, v vestibule.

Figure 83. Peronia verruculata (unit 3), Peninsular Malaysia, Langkawi, [976] (USMMC 00051) A digestive system, dorsal view, the arrow indicates the orientation of the transitional loop B posterior, hermaphroditic (female) reproductive system C anterior, male, copulatory apparatus. Scale bars: 5 mm (A), 3 mm (B), 4 mm (C). Abbreviations: ag accessory penial gland, dd deferent duct, ddg dorsal digestive gland, fgm female gland mass, hg hermaphroditic gland, i intestine, ms muscular sac, ov oviduct, pdg posterior digestive gland, ps penial sheath, rm retractor muscle, rs receptaculum seminis, sp spermatheca, st stomach, v vestibule.

Figure 84. Peronia verruculata (unit 4) A lectotype, Paraperonia gondwanae, India, Mumbai (MNHN-IM- 2000 - 33681) B-D Pakistan, [6164] (MNHN-IM- 2019 - 1384) A digestive system, dorsal view, the arrow indicates the orientation of the transitional loop B digestive system, dorsal view C posterior, hermaphroditic (female) reproductive system D anterior, male, copulatory apparatus. Scale bars: 4 mm (A, C), 5 mm (B, D). Abbreviations: ag accessory penial gland, dd deferent duct, ddg dorsal digestive gland, fgm female gland mass, hg hermaphroditic gland, i intestine, ms muscular sac, ov oviduct, pdg posterior digestive gland, ps penial sheath, rm retractor muscle, rs receptaculum seminis, sp spermatheca, st stomach, v vestibule.

Figure 85. Digestive system, dorsal view, Peronia verruculata (unit 5). The arrow indicates the orientation of the transitional loop A lectotype, Scaphis gravieri, Mayotte (MNHN-IM- 2000 - 33695) B Madagascar [3144] (MNHN-IM- 2019 - 1611) C Madagascar [3231] (MNHN-IM- 2019 - 1610). Scale bars: 2 mm (A), 4 mm (B), 5 mm (C). Abbreviations: ddg dorsal digestive gland, i intestine, pdg posterior digestive gland, st stomach.

Figure 86. Digestive system, dorsal view, Peronia verruculata (Red Sea). The arrow indicates the orientation of the transitional loop A lectotype, Onchidium verruculatum, Red Sea (MNHN-IM- 2000 - 22941) B lectotype, Peronia anomala, Red Sea (MNHN-IM- 2000 - 33678) C lectotype, Onchidium durum, Red Sea (MNHN-IM- 2000 - 33698) D paralectotype, Paraperonia gondwanae, Red Sea (MNHN-IM- 2000 - 33684) E paralectotype, Paraperonia gondwanae, locality unknown (MNHN-IM- 2000 - 33688) F Red Sea, spm 1 (ZMH 27472 / 4). Scale bars: 5 mm (A, D), 4 mm (B, E), 3 mm (C, F). Abbreviations: ddg dorsal digestive gland, i intestine, pdg posterior digestive gland, st stomach.

Figure 87. Radula, Peronia verruculata (unit 1), Vanuatu [5481] (MNHN-IM- 2013 - 62393) A rachidian and innermost lateral teeth B lateral teeth C outermost lateral teeth D lateral teeth, frontal view. Scale bars: 20 μm (A), 100 μm (B), 10 μm (C, D). Abbreviations: 1 llt first left lateral tooth, 1 rlt first right lateral tooth, 2 llt second left lateral tooth, 2 rlt second right lateral tooth, bls basal lateral spine, hlt hook of a lateral tooth, mc median cusp, rt rachidian tooth.

Figure 88. Radula, Peronia verruculata (unit 1), Indonesia A, B Seram [2870] (UMIZ 00169) C-F Lombok [2987] (UMIZ 00168) A left half rows of teeth B rachidian and innermost lateral teeth C rachidian and innermost lateral teeth D rachidian and lateral teeth E outermost lateral teeth F lateral teeth. Scale bars: 200 μm (A), 30 μm (B, C), 60 μm (D), 40 μm (E), 100 μm (F).

Figure 89. Radula, Peronia verruculata (unit 2), Indonesia, Sumatra A-D [1795] (UMIZ 00180) E [1746] (UMIZ 00178) A rachidian and innermost lateral teeth B rachidian and innermost lateral teeth C lateral teeth D outermost lateral teeth E lateral teeth, frontal view. Scale bars: 40 μm (A, D), 80 μm (B), 100 μm (C), 60 μm (E).

Figure 90. Radula, Peronia verruculata (unit 3), Peninsular Malaysia A-C [976] (USMMC 00051) D [975] (USMMC 00064) A rachidian and innermost lateral teeth B rachidian and lateral teeth C outermost lateral teeth D lateral teeth, frontal view. Scale bars: 20 μm (A, C), 100 μm (B), 10 μm (D).

Figure 91. Radula, Peronia verruculata (unit 4), Pakistan A-C [6164] (MNHN-IM- 2019 - 1384) D [6165] (MNHN-IM- 2019 - 1385) A rachidian and innermost lateral teeth B lateral teeth C outermost lateral teeth D outermost lateral teeth. Scale bars: 20 μm (A, B), 10 μm (C), 40 μm (D).

Figure 92. Radula, Peronia verruculata (unit 5), Madagascar A-C [3231] (MNHN-IM- 2019 - 1610) D Mozambique [5510] (MNHN-IM- 2013 - 62398) A rachidian and innermost lateral teeth B lateral teeth C outermost lateral teeth D lateral teeth, frontal view. Scale bars: 20 μm (A, C), 100 μm (B), 30 μm (D).

Figure 93. Radula, Peronia verruculata, Red Sea, spm 3 (ZMH 27472 / 4) A rachidian tooth B rachidian and innermost lateral teeth C lateral teeth D lateral teeth E outermost lateral teeth F lateral teeth. Scale bars: 10 μm (A), 30 μm (B), 20 μm (C, E), 100 μm (D), 60 μm (F).

Figure 94. Reproductive system, Peronia verruculata (unit 1) A immature, posterior, hermaphroditic (female) reproductive system, Australia, Queensland [2622] (MTQ) B posterior, hermaphroditic (female) reproductive system, Vietnam [5621] (ITBZC IM 00021) C posterior, hermaphroditic (female) reproductive system, Indonesia, Sulawesi [2127] (UMIZ 00170) D anterior, male, copulatory apparatus, same as C. Scale bars: 1 mm (A), 4 mm (B), 3 mm (C), 5 mm (D). Abbreviations: ag accessory penial gland, dd deferent duct, ddg dorsal digestive gland, fgm female gland mass, hg hermaphroditic gland, i intestine, ms muscular sac, ov oviduct, pdg posterior digestive gland, ps penial sheath, rm retractor muscle, rs receptaculum seminis, sp spermatheca, st stomach, v vestibule.

Figure 95. Reproductive system, Peronia verruculata (unit 5), Madagascar A posterior, hermaphroditic (female) reproductive system, only the spermatheca, the deferent duct, and the oviduct, [3143] (MNHN-IM- 2019 - 1611) B posterior, hermaphroditic (female) reproductive system, [3231] (MNHN-IM- 2019 - 1610) C anterior, male, copulatory apparatus, same as B. Scale bars: 5 mm (A), 3 mm (B), 4 mm (C). Abbreviations: ag accessory penial gland, dd deferent duct, fgm female gland mass, hg hermaphroditic gland, ms muscular sac, ov oviduct, ps penial sheath, rm retractor muscle, rs receptaculum seminis, sp spermatheca, v vestibule.

Figure 96. Reproductive system, Peronia verruculata, Red Sea, spm 1 (ZMH 27472 / 4) A posterior, hermaphroditic (female) reproductive system B anterior, male, copulatory apparatus. Scale bars: 2 mm (A), 4 mm (B). Abbreviations: Abbreviations: ag accessory penial gland, dd deferent duct, fgm female gland mass, hg hermaphroditic gland, ms muscular sac, ov oviduct, p penis, ps penial sheath, rm retractor muscle, rs receptaculum seminis, sp spermatheca.

Figure 97. Penial hooks, Peronia verruculata (unit 1) A Australia, Queensland [2622] (MTQ) B Indonesia, Halmahera [5068] (UMIZ 00166) C Papua New Guinea, Madang [5469] (MNHN-IM- 2013 - 12010) D same as B; E Indonesia, Seram [2870] (UMIZ 00169) F same as C. Scale bars: 4 μm (A, B), 20 μm (C), 30 μm (D), 3 μm (E, F).

Figure 98. Penis and penial hooks, Peronia verruculata (unit 2), Indonesia, Sumatra A, B [1746] (UMIZ 00178) C, E [1795] (UMIZ 00180) D, F [1797] (UMIZ 00180). Scale bars: 60 μm (A), 6 μm (B, E, F), 20 μm (C, D).

Figure 99. Penial hooks, Peronia verruculata (unit 3), Peninsular Malaysia A, B [2547] (USMMC 00065) C, D [975] (USMMC 00064). Scale bars: 40 μm (A, C), 20 μm (B), 6 μm (D).

Figure 100. Penial hooks, Peronia verruculata (unit 4), Pakistan A-C [6164] (MNHN-IM- 2019 - 1384) D [6165] (MNHN-IM- 2019 - 1385). Scale bars: 20 μm (A), 10 μm (B-D).

Figure 101. Penial hooks, Peronia verruculata (unit 5) A-C Madagascar [3144] (MNHN-IM- 2019 - 1611) D, E Madagascar [3231] (MNHN-IM- 2019 - 1610) F Mozambique [5510] (MNHN-IM- 2013 - 62398). Scale bars: 6 μm (A), 10 μm (B, E), 20 μm (C), 100 μm (D), 4 μm (F).

Figure 102. Penis and penial hooks, Peronia verruculata, Red Sea A-C spm 1 (ZMH 27472 / 4) D spm 2 (ZMH 27472 / 4) E, F spm 4 (ZMH 27472 / 4). Scale bars: 300 μm (A), 10 μm (B), 30 μm (C), 20 μm (D, E), 4 μm (F).

Figure 103. Accessory penial gland spine, Peronia verruculata (unit 1) A-G Indonesia H Singapore A Halmahera [5068] (UMIZ 00166) B Ambon [2729] (UMIZ 00162) C Lombok [2987] (UMIZ 00168) D Sulawesi [2127] (UMIZ 00170) E same as A; F same as B; G same as C; H [991] (ZRC. MOL. 10497). Scale bars: 300 μm (A-D), 20 μm (E), 10 μm (F), 15 μm (G), 150 μm (H).

Figure 104. Accessory penial gland spine, Peronia verruculata (unit 1) A Vietnam [5621] (ITBZC IM 00021) B Papua New Guinea [5469] (MNHN-IM- 2013 - 12010) C Vanuatu [5481] (MNHN-IM- 2013 - 62393) D New Caledonia [6214] (MNHN-IM- 2019 - 1593) E same as A; F same as B; G same as C; H same as D. Scale bars: 300 μm (A, B, D), 200 μm (C), 10 μm (E-G), 20 μm (H).

Figure 105. Accessory penial gland spine, Peronia verruculata (unit 2), Indonesia, Sumatra A, E [1797] (UMIZ 00180) B, F [1795] (UMIZ 00180) C, G [1796] (UMIZ 00180) D [1746] (UMIZ 00178). Scale bars: 300 μm (A-C), 10 μm (D-G).

Figure 106. Accessory penial gland spine, Peronia verruculata (unit 3) A-C, E-I, K, L Peninsular Malaysia D, J Singapore A [975] (USMMC 00064) B [976] (USMMC 00051) C [977] (USMMC 00064) D [989] (ZRC. MOL. 16070) E [2546] (USMMC 00065) F [2547] (USMMC 00065) G same as A; H same as B; I same as C; J same as D; K same as E; L same as F. Scale bars: 300 μm (A-F), 20 μm (G-L).

Figure 107. Accessory penial gland spine, Peronia verruculata (unit 4), Pakistan A, C [6164] (MNHN-IM- 2019 - 1384) B, D [6166] (MNHN-IM- 2019 - 1386). Scale bars: 300 μm (A, B), 20 μm (C, D).

Figure 108. Accessory penial gland spine, Peronia verruculata (unit 5) A Madagascar [3231] (MNHN-IM- 2019 - 1610) B Madagascar [3144] (MNHN-IM- 2019 - 1611) C Mozambique [5510] (MNHN-IM- 2013 - 62398) D same as A; E same as B; F same as C. Scale bars: 300 μm (A-C), 10 μm (D-F).

Figure 109. Accessory penial gland spine, Peronia verruculata, Red Sea A, E spm 1 (ZMH 27472 / 4) B, F spm 2 (ZMH 27472 / 4) C, G spm 3 (ZMH 27472 / 4) D, H spm 4 (ZMH 27472 / 4). Scale bars: 300 μm (A, C, D), 400 μm (B), 10 μm (E), 20 μm (F-H).