This belongs to the same group of species as tridens, quadra, spathatula, and concamerata, which last represents it on the Californian coast. In its posterior cup-like appendages, it resembles Talona clausa from the Gambia. The shell is extremely thin, shewing inside a row of oblong tubercles impressed from without on the line separating the anterior and posterior portions, as well as the anterior ridges. These are closely set, strong, and waring; and passing over the medial depression at an angle slightly widening as the shell becomes adult, are continued, concentric and straight, "gradually fading as they approach the posterior extremity. This is covered with a thick epidermis, ending in a short double cup, which is bilobed outside and simple within. The adult closing of the valves is carried in a flat expansion round to the umbos. The largest specimen measures, with the cup, long. 0' 9, led. 1,85, alt. 8,6.

In hard clay and loose stones at low water, Mexico (Mazatlan), Ecuador Monte Christi (Guayaquil)