Abra sinica sp . nov, (Fig .1)

Shell small, rather thick, compressed, inequilateral, almost equivalve, but slightly twisted to right posteriorly and elongated oval in shape; umbo low, situated at posterior third of shell; anterior part larger and wider than posterior, rounded anteriorly and narrowed to posterior end; anterior dorsal margin convex, posterior dorsal margin slightly concave, ventral margin gently curved; surface of shell smooth and polished and colored white to light rose, with weak growth lines.

Inner surface of shell with weak radial lines, the anterior adductor scar elongated, the posterior circular in shape; pallial sinus very deep, almost extending to anterior adductor scar, its lower border confluented with pallial line; the hinge plate of left valve with one large and bifid anterior cardinal tooth; right valve with one small anterior cardinal tooth and one large and bifid posterior cardinal tooth; left valve without lateral tooth, right valve with one anterior lateral tooth longer than the posterior; the ligament stronger than the resilium behind the cardinal teeth.

Measurement (mm) length heigt breadth

8.0 6.0 2.4

9.1 6.5 2.4

6.9 4.4 2.0

6.8 4.5 2.0

Holotype (11 - 1003) Collected from 31°30′ N, 122°40 ′ E. Fine sandy bottom of 28m depth, July 12, 1986. Paratype (10 - 982) Collected from 32°00′ N, 122°45′ E. Fine sandy bottom of 32m depth, June 30, 1986.

Locality Changjiang River Estuary. Fine sandy bottom of 28 - 35m depth. A total of 1002 specimens in 24 samples were collected.

Abra kurodai Habe, 1961 is related to this new species in shape, but the former has shallow pallial sinus partly confluented with pallial line.

The type specimens are deposited in the Institute of Oceanology, Chinese Academy of Sciences, in Qingdao.