Description:
The valves of angelwing clams are generally equal in size and extremely fragile.  Color is white overall, with shades of pink sometimes observed. Body shape is oval and elongate, narrowing towards the posterior end. Valves have umbones which are covered by a chitinous plate extending 1/4 the shell length from the anterior end. Valves are patterned with radial riblets, which are sharp and angular in the anterior, and broader in the posterior.  Inside the valves, behind the umbones, is a thick, winged plate that lies transverse to the plane of the valves. C. costata grows 4 - 8 inches and is noted for its rapid growth rate.

Habitat:
Angelwing clams are most common in the low intertidal zone, at or just below the low tide line, where they can burrow to a depth of approximately 3 feet in soft sand or muddy substrata.

Range:
C. costata occurs along the eastern U.S. coast from Massachusetts to Brazil. It is common along Florida's west coast, but is patchily distributed along much of the east central Florida coast.