Arcopsis sculptilis ( Reeve, 1844 )

Raines, Bret & Huber, Markus, 2012, 3217, Zootaxa 3217, pp. 1-106 : 19-20

Arcopsis sculptilis ( Reeve, 1844)

Figures 8 D–F

Arca sculptilis Reeve, 1844 : sp. 118, pl. 17, fig. 118.

Arcopsis sculptilis ( Reeve, 1844) — Huber, 2010: p. 147, fig. 8.

Barbatia (Acar) — Luke, 1995: p. 106.

Material examined. Several articulated specimens and nearly fifty single valves (4 to 8.5 mm) (BK), including material from the 1957/58 Downwind Expedition ( SIO Benthic Collection, M1447), plus specimens from the Red Sea ( MHU), Philippines ( MHU) and Borneo ( MHU).

Diagnosis. Shell small, subovate, equivalve, inflated, not fragile. Umbones elevated. Posterior end obtusely rounded, anterior rounded. Exterior surface latticed with raised fine radial and commarginal threads. Diamondshaped ligament. Hinge consisting of numerous teeth separated under the umbones, slanted, and larger distally. Color white to pale tan.

Remarks. The EI material was compared with Red Sea, Philippine and Borneo material, which showed the same variations in shape and sculpture. Currently, this is the only true Arcopsis species known from the Indo- Pacific. Unusual is the fact, that some of the EI specimens actually exceed the norm in size (WRS 8.5 mm from Anakena). However, this may be due to restricted collecting elsewhere. The Barbatia (Acar) species noted by Luke (1995) from the SIO Benthic Collection, M1447 ( Fig. 8 F) represents this species as well.

Habitat. Commonly found at many locations around EI and SyG, in sand, from 10–180 m.

Distribution. Arcopsis sculptilis is a widely distributed species throughout the Indo-Pacific including the Red Sea. However, it is not known from the Hawaiian Islands, New Zealand or the Kermadec Islands. Easter and Salas y Gómez Islands are now considered a range extension— E4.