Retusa insolita, Valdés, 2008

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 735-736

Retusa insolita n. sp.

Figs 73E, F, 74

TYPE MATERIAL. — Holotype MNHN 20410 and 9 paratypes MNHN 20411-20418, 5 paratypes LACM 3002 .

TYPE LOCALITY . — Norfolk Ridge , 23°09’S, 167°43’E, 975-1005 m [BIOCAL: stn DW 53 ] .

MATERIAL EXAMINED. — North of New Caledonia. MUSOR- 1 dd, paratype ( MNHN 20416 ) . — BIOGEOCAL: stn DW 313 , STOM 4 : stn DC 168, 18°48’S, 163°11’E, 720 m, 1 dd, paratype 20°59’S, 166°59’E, 1600-1640 m, 1 dd, paratype ( MNHN 20417 ). ( MNHN 20411 ) . — BATHUS 4 : stn DW 914 , Grand Passage, — BATHUS 3 : stn DW 793 , Mont J, 23°47’S, 169°49’E, 731-751 18°49’S, 163°15’E, 600-616 m, 1 dd, paratype ( MNHN 20412 ). m, 1 dd, paratype ( MNHN 20418 ) .

New Caledonia proper. BATHUS 2: stn CP 755, Passe de Dumb- Vanuatu. MUSORSTOM 8: stn DW 987, 19°23’S, 169°35’E, 1040- éa, 22°22’S, 166°14’E, 495 m, 1 dd, paratype ( MNHN 20413). 1050 m, 1 dd; stn DW 1128, 16°02’S, 166°38’E, 778-811 m, 5 dd, Norfolk Ridge. BIOCAL: stn DW 53, 23°09’S, 167°43’E, 975- paratypes ( LACM 3002).

1005 m, 1 dd, holotype ( MNHN 20410; Figs 73E, F); stn DW 56, Wallis and Futuna. MUSORSTOM 7: stn DW 507, Futuna Is- 23°35’S, 167°12’E, 695-705 m, 1 dd, paratype ( MNHN 20414); land, 14°20’S, 178°07’W, 419-425 m, 1 dd; stn DW 557, Banc stn DW 70, 23°25’S, 167°53’E, 965 m, 2 dd, paratypes ( MNHN Tuscarora, 11°48’S, 178°18’W, 600-608 m, 1 dd.

20415). Tonga. BORDAU 2: stn DW 1585, Vava‘u Islands, 18°33’S, Loyalty Ridge. BIOCAL: stn KG 06, 20°35’S, 166°53’E, 735 m, 173°57’W, 578 m, 5 dd.

DISTRIBUTION. — Collected from New Caledonia, Tonga, Vanuatu and Wallis and Futuna (Fig. 74), in 425-1600 m.

DESCRIPTION. — Shell morphology. Length 7 mm, width 4 mm (holotype). Shell solid, elongate, with nearly parallel sides (Fig. 73E). Body whorl large, between 3/4 to 9/10 of the shell length. Spire short and wide, apically truncated, with 1.5 short whorls. Apex deeply umbilicate (Fig. 73F). Anterior end of the shell rounded. Aperture shorter than the shell, wider anteriorly and narrowing gradually at about 1/3 of its length. Columellar margin slightly thickened. Columella simple, with no folds. Umbilicus closed. Sculpture of a number of faint growth lines. On the posterior end of the spire there is a distinctive pattern of curved and well-marked growth lines. Colour uniformly whitish to pale brown.

Anatomy. Unknown. All shells collected lacked soft parts.

REMARKS. — The shell morphology of Retusa insolita is very similar to that of Cylichna vortex Dall, 1881 , described from the northeast Atlantic in 596-2480 m ( Dall 1881). Differences between these two species include the longer shell of R. insolita with a wider posterior end of the aperture and the presence of an apical umbilicus. Study of the anatomy of C. vortex has shown that it belongs to Cylichna (Bush 1893) .

This species is here placed in Retusa , based on the shell morphology, pending availability of complete specimens.

ETYMOLOGY. — From the Latin insolitus (odd, strange), in references to the unique shell shape of this species.

FIG. 74. Collection localities of species of Retusa Brown, 1827 in the southwest Pacific: °, Retusa waughiana Hedley, 1899 . Z, Retusa diaphana n. sp. •, Retusa insolita n. sp.