Sunetta concinna
Similar to Sunetta scripta. Sunetta concinna can be distinguished by its slightly anterior umbo. Sunetta scripta has an elongate anterior dorsal margin and a slightly posterior umbo.
The overall shape is trigonal ovate. The anterior dorsal margin is slightly concave, while the posterior dorsal margin is slightly convex. The margin is pointed posteriorly, where the ventral and posterior dorsal margins meet. The posterior half of the flank is slightly more inflated than the anterior. The valves are the same size and shape (equivalve), and there is no gape when they are closed. The sculpture consists of growth lines only. The lunule is lightly impressed, defined by a fine shallow groove and extends 2/3 of the anterior dorsal margin. The umbo is pointed slightly to the anterior. The escutcheon is deeply sunken.
The external color is white or yellow. Typically, there are light or dark brown tent patterns. Some growth lines may be marked by a purple coloration. The internal color is white, and there may be purple coloration concentrated at the anterior and posterior ends of the pallial line.
The ligament is external, extends 1/4 of the posterior dorsal margin and is supported by nymphal ridges. On the left valve, there are three cardinal teeth. The teeth (2a, 2b, 4b) are not bifid, 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 (3a, 1, 3b), none of which are bifid. There are also two anterior lateral teeth (A1, A3) on the right valve. There are crenulations on the posterior and ventral margins, and they become weaker at the anterior. The anterior and posterior muscle scars are similar in area, but the posterior is rounder than the anterior. The pallial sinus is pointed and extends to the posterior tooth in length.