Retusa sp. 3

Valdés, Ángel, 2008, Deep-sea “ cephalaspidean ” heterobranchs (Gastropoda) from the tropical southwest Pacific, Mémoires du Muséum national d'Histoire naturelle 196, pp. 587-792 : 742

Retusa sp. 3

Figs 77A, B, 78

MATERIAL EXAMINED. — Indonesia. KARUBAR: stn DW 03 , Kai Islands , 05° 48’S, 132°13’E, 278-301 m, 1 dd .

Fiji. MUSORSTOM 10: stn CP 1341, Bligh Water, 16°53’S, 177°48’E, 500-614 m, 1 dd (Figs 77 A, B).

DISTRIBUTION. — Material herein collected from Fiji and Indonesia (Fig. 78), in 301-500 m.

DESCRIPTION — Shell morphology. Length 3 mm, width 1.5 mm (largest specimen examined). Shell solid, oval, with convex sides (Fig. 77A). Only 1 whorl visible, forming the entire shell. Anterior end of the shell rounded. Umbilicus narrow. Aperture long, wide anteriorly, narrowing gradually at about 1/3 of its length. At its apical end, the aperture bends over the apex of the shell and the parietal wall forms a blunt prolongation that completely covers the apex (Fig. 77B). Columellar margin thickened near the anterior end of the shell. Sculpture of numerous, faint and densely concentrated spiral grooves crossed by fine growth lines all over the shell surface. Colour uniformly shiny whitish.

Anatomy. Unknown. The single shell collected lacked soft parts.

REMARKS. — Retusa sp. 3 is similar in shell morphology to Retusa abyssicola n. sp., but has a much shorter shell with more convex sides, and a narrow umbilicus. Differences between Retusa sp. 3 and Retusa crispula include the absence of an apical umbilicus and the presence of a sculpture of spiral grooves and growth lines in the former, absent in the latter.

Retusa sp. 3 appears to be distinct from other Indo-Pacific species of the genus, but it is not named here because of the lack of enough material for study. This species is placed in Retusa , pending availability of complete specimens.