Shell thin, equivalve but inequilateral, ovate, shortly produced to the anterior end which is truncated obliquely and elongated to the posterior end which is gaping; moderately convex; surface sculptured with many fine radial threads all over and has some undulations of growth lines ; a very weak flexure runs from the umbo to the antero-ventral corner ; umbo situates at the anterior third of the dorsal line and is hardly elevated above the dorsal line ; ligament external and located just behind the umbo; no hinge teeth present; the interior pearly and polished ; muscle scars rather small and the mantle line with a sinus which is not so deep.
Height 22.3 mm., length 29. 0 mm. and breadth 15.5 mm. (type specimen figured)
Type locality: Wakayama Pref., Honshu.
Remarks: This second species of the genus Pholadomya from Japan differs from Ph. pacifica Dall in lacking the strong radial cords on the middle part of the surface of the shell which is truncated obliquely at the anterior end. Ph. loveni Jeffreys from the North Atlantic is also a closely allied species, but has a more globose shell with the distinctly prominent umbo.