Circenita varia
Similar to Circenita callipyga. Circenita varia is not as elongate anterio-posteriorly, and it is taller; its posterior margin is also more truncated than that of C. callipyga.
The overall shape is ovate. The posterior margin is truncated. Both the anterior and posterior dorsal margins are nearly straight. The valves are equal in size and shape (equivalve), and there is no gape when they are closed. Sculpture consists of growth lines and comarginal ribs that become stronger as the animal grows.The ribs may merge at the anterior and posterior ends of the flank. The lunule is lightly impressed, defined by a fine shallow groove, and extends half the anterior dorsal margin. The umbo is subcentral and the beaks point slightly to the anterior. The ribs fade at the escutcheon, which extends 2/3 of the posterior dorsal margin.
The exterior surface is white.There may be brown comarginal stripes, radial stripes or tent marks. There may also be purple or dark brown comarginal stripes near the ventral margin. The nepioconch may be white, pink or purple in coloration. The interior is white. Typically, there is a pink or purple blush through the interior. There may also be dark brown coloration at the anterior and/or posterior margins, as well as under the nymph and/or the lunule.
The ligament is external, extends half the posterior dorsal margin and is supported by nymphal ridges. On the left valve, there are three cardinal teeth (2a, 2b, 4b), none of which are bifid. The central tooth (2b) may have a slightly rugose texture, and the posterior tooth (4b) is fused with the nymph. There is also one anterior lateral tooth (A2) on the left valve. On the right valve, there are three cardinal teeth. The anterior tooth (3a) is not bifid; the central (1) and posterior (3b) teeth are lightly bifid. There are also two anterior lateral teeth (A1, A3) on the right valve, as well as a very fine ridge that runs parallel to the posterior dorsal margin. The posterior adductor muscle scar is slightly larger than the anterior, and the pallial sinus is absent or extremely short.