Western bay scallop

Argopectin irradians amplicostatus

Family Pectinidae - scallops

Bivalve (2 shells); shell circular, fan-like, with extensions or wings on either side of beaks, wings equal in length when not broken or worn down; moderately inflated, right shell more inflated than left; color brown to gray on left (top) shell, lighter in between ribs; right (bottom) shell white, no markings; 12-17 strong radial ribs; fine concentric lines, more prominent between ribs in larger shells, runs over ribs in smaller shells; ventral edges scalloped; live specimens with blue eyes and tentacle along edge of mantle.
Similar Species
The calico scallop has a light background with various mottling and a reddish upper interior. The bay scallop is usually a solid color with white interior and the right shell (which is usually white) is distinctly more convex than the left shell. Also, the bay scallop has 12-17 ribs while the calico scallop has 17-23 (excluding the wings).
Bays, on mud and sandy bottoms, free-living, does not burrow
Maximum Size
10.2 cm (4 in)
Other Common Names
Previous Scientific Names
There are 3 varieties of A. irradians in the Gulf of Mexico. A. irradians amplicostatus does not occur east of the Mississippi River.