These species have a shell that is usually about 17mm x
14mm x 5mm. The shells range from small to medium; they are
subtrigonal, more or less elongate, almost equilateral with a polygonal
ventral margin, and the ears are large and hinge line straight. Both
valves are decorated with 16-17 radiating ribs. These species
can be found in the Glen Rose Formation, Mt. Bonnell; and Walnut Clay, Mt.
Barker, Austin, Texas.