Meretrix lusoria
Similar to Meretrix meretrix. Meretrix lusoria is distinguishable by its lighter, thinner shell and its elongate posterior margin. M. meretrix is rounder and much more robust.
Similar to Meretrix ovum. Meretrix lusoria can be distinguished by its trigonal shape and elongate posterior dorsal margin.
Similar to Meretrix petechialis. Meretrix lusoria is distinguishable by its more elongate posterior margin, as well as its less inflated valves and less robust hinge plate and teeth.
The overall shape is trigonal ovate. The posterior margin is more pointed than the anterior, and the ventral margin is rounded. The valves are the same size and shape (equivalve), and there is no gape when they are closed. The posterior half of the flank is slightly more inflated than the anterior half. Sculpture consists of growth lines only. The lunule is lightly impressed, defined by a fine shallow groove, and extends 3/4 of the anterior dorsal margin. The commissural margin is slightly raised at the center of the lunule. The umbo is slightly anterior. The escutcheon is not well defined. The commissural margin is also slightly raised at the posterior dorsal margin.
The exterior surface is white, and typically has brown tent marks, radial stripes and/or comarginal stripes. The periostracum is dark brown or dirty gray. The posterior dorsal margin may be dark brown in color. The interior color is white, and there may be purple rays of coloration at the posterior and anterior, typically close to the margin.
The ligament is external, extends 1/3 of the posterior dorsal margin, and is supported by nymphal ridges. On the left valve, there are three cardinal teeth. The anterior (2a) and central (2b) teeth are not bifid, and the posterior tooth (4b) is fused with the nymphal ridge. The shallow groove between the nymph and the posterior tooth has fine, vertical striations. There is also one anterior lateral tooth (A2) on the left valve. On the right valve, there are three cardinal teeth. The anterior (3a) and central (1) are not bifid, and the posterior (3b) is lightly bifid. The nymph has very fine vertical striations. There are also two anterior lateral teeth (A1, A3) and a fine ridge that runs parallel to the posterior dorsal margin on the right valve. The posterior adductor muscle scar is slightly more rounded than the anterior. The pallial sinus is very short, rounded and extends to the posterior end of the hinge plate in length.