Argopecten irradians concentricusis a member of the family Pectinidae. The bay scallop is difficult to distinguish from the queen scallop (Chlamys opercularis) and the calico scallop (Argopecten gibbus). For the bay scallop, the shell is right convex (the right valve is more rounded than the left) (Fay et al. 1983). The shell of A. irrradians concentricus is broadly fan shaped with more than 14 radial ribs (Fay et al. 1983, Mikkelsen and Bieler 2008). Shells are symmetric and vary considerably in color. They usually have a molted pattern incorporating dark grey, black, or brown with orange, red, or yellow hues (Fay et al. 1983).