Leptoconchus incrassa sp. nov.

(Figs. 3, 42–44)

Etymology. The specific epithet reflects that the species has been found exclusively in corals of Ctenactis crassa . For the purposes of nomenclature, it is herewith declared (under ICZN 1999 Article 26) as not to be treated as a Greek, Latin or latinized word; thus, the spelling presented here is to remain unchanged.

Type material. Holotype female (RMNH 102726), found in the mushroom coral Ctenactis crassa; Palau, NE of Ngeremdiu, Lighthouse Reef, backreef, 07°17′11″N 134°27′26″E.

Paratypes. Palau. NE of Ngeremdiu: type locality (RMNH 102727 /e found with holotype, 102728/1sn: m in same coral as holotype, RMNH 102729 /1sn: f, 102730/1sh: f, 102731/ 2sn: m&f, 1sh: f) ; SE of Ngederrak Reef, Halimeda flat, 07° 17′21″N 134°29′04″E (RMNH 102732 /1sn: f+e, 1sh: f) .

Thailand. Phi Phi Islands: NE Koh Phi Phi Le, Pi Le Bay, near cave, 07°41′43″N 98°45′57″E (RMNH 95886 */1sn: f, 2sh: 2f); S Koh Phi Phi Le, Loh Samah, 07°40′28″N 98°46′ 10″E (RMNH 95978 /2sn: m&f+e); Hin Daeng, 07°08′59″N 98°49′25″E (RMNH 95983 /1sn: f); E Koh Phi Phi Don, Poh Cape, Hin Phae, 07°43′30″N 98°47′17″E (RMNH 96015 /2sn: m&f+e); S Koh Phi Phi Don, S Tongsai Bay, 07°43′14″N 98° 46′13″E (RMNH 96006 /1sn: f, 1sh: f) .

Indonesia. NE Kalimantan: Berau Islands, SW Derawan Island, 02º16′18″N 118º15′08″E (RMNH 102733 /1sn: f) .

N Sulawesi: SW Gorontalo, 00°21′31″N 124°03′14″E (RMNH 102734 */2sn: m&f+e, 3sh: sf) .

Diagnosis. Among the Leptoconchus species with reduced and variable morphological characters and associated with fungiid corals, L. incrassa sp. nov. is differentiated by a unique combination of nucleotides in the Cytochrome Oxidase I barcoding sequence (GB: EU215804, EU215805), as indicated by underlined letters in Fig. 48.

Shell. Holotype female (Figs. 42, 43) H 15.7 mm, W 22.1 mm; columellar callus not conspicuously expanded; palatal part of outer lip gradually passing into shell base. In male shell (Fig. 44), callus covers most of last whorl and obtuse angle present at shell base. H and W of largest female shell 23.1 mm and 29.0 mm, respectively, versus 10.3 mm and 10.7 mm for largest male shell (found with holotype). Apical part of female shell protrudes somewhat above apertural edge (Fig. 42), hardly protrudes in male (Fig. 44).

Habitat. The snails and their egg capsules were found at 8–31 m depth, exclusively with the mushroom coral species Ctenactis crassa (Dana, 1846) . The siphon pores are located on the underside of the corals.

Distribution. The range of Leptoconchus incrassa extends from Thailand to Palau and Indonesia.