Shell description. - The shell is elongated, equilaterally triangular, thin, fragile, translucent, and white in colour. The surface is covered with a thin light brown periostracum. The exterior surface is smooth with weak, closely spaced irregular concentric growth lines that form weak ridges near the umbones. The anterior dorsal margin is almost straight or slightly convex, terminating in a widely rounded anterior margin. The posterior dorsal edge is weakly convex, and the posterior margin is truncated. There is a prominent keel radiating from the umbones and terminating at the postero-ventral margin. The umbones are small, pointed, tilting toward the anterior and placed at the midline. The lunule is narrow. The shell interior is glossy white. The adductor muscle scars are small, the posterior being more rounded than the anterior. The pallial sinus is rounded, almost reaching the midline, about as deep as it is high, and partly confluent with the pallial line. The resilifer is large and deep. The left valve has one anterior and one posterior lateral tooth, both of which are well developed. The right valve has two anterior and two posterior lateral teeth, but the dorsal most anterior lateral tooth in the right valve is reduced to a shortened ridge.

Distribution. - This species occurs widely in the tropical Indo-Pacific region, including China, Japan, the Philippines, and Indonesia (Habe, 1968; Okutani, 2000; Qi, 2005).

Remarks. - Disjointed valves were occasionally encountered among debris deposited at the shore high tide line during the survey.