Semelangulus nebulosus Dall, Bartsch & Rehder, 1938

Raines, Bret & Huber, Markus, 2012, 3217, Zootaxa 3217, pp. 1-106 : 79-81

Semelangulus nebulosus Dall, Bartsch & Rehder, 1938

Figures 40 H–K

Semelangulus nebulosus Dall et al., 1938: p. 180 , pl. 47, figs. 5–8.

Semelangulus nebulosus Dall et al., 1938 — Rehder & Randall, 1975: p. 35.

Semelangulus crebrimaculatus (Sowerby, [sic] 1868)— Preece, 1995: p. 351. Material examined. Over fifty articulated specimens and single valves (2.8 to 5 mm) (BK), as well as several specimens from Pitcairn Island (BK).

Diagnosis. Shell small (up to 5 mm in length), donaciform, stout and equivalve. Posterior end obliquely truncate; anterior end well rounded. Umbones elevated. Surface very smooth, glossy, except for some weak irregular commarginal sculpture. Hinge consisting of distinctly pronounced dentition with two clear laterals in the RV, while in the LV they are nearly obsolete. Color milky white and mottled with whiter spots.

Remarks. Kay (1979) synonymized Semelangulus nebulosus as well as S. dichrous , S. diodorus and S. oahuensis Dall, Bartsch & Rehder, 1938 , to S. crebrimaculatus G.B. Sowerby II, 1867 . Although the other species may indeed be synonymous, we believe S. nebulosus to be very distinct. It is unique by its rather truncate and comparatively higher shape, by the milky white color and by the comparatively weak commarginal sculpture. It is the smallest of the Hawaiian species. Semelangulus nebulosus is here considered a valid species and a new record for EI, accepted by A. Langleit, (pers. comm., 2010).

Habitat. Silty mud at 15 m in cave, on northern coast off Hanga-Teo, EI. 27 o 03’37” S, 109 o 21’58” W.

Distribution. Semelangulus nebulosus is known from the Hawaiian Islands, Pitcairn Islands, and now a new record for Easter Island— E5.