Subgenus (Petrasma) W. H. Dall, 1908

(3-3-2-0-3-2-0-1-2-0-0-0-0)
Ref. Abbott, 1974 p 420

borealis J. G. Totten, 1834 [T]
(3-3-2-0-3-2-0-1-2-1-0-0-0)
Boreal Awning Clam
Size 2"-3" long
Ref. Abbott, 1974 p 420 bw

occidentalis G. P. Deshayes, 1857
(3-3-2-0-3-2-0-1-2-2-0-0-0)
West Indian Awning Clam
Size 0.25" long
Ref. Abbott, 1974 p 420 bw

panamensis W. H. Dall, 1908
(3-3-2-0-3-2-0-1-2-3-0-0-0)
Panama Awning Clam
Size 1"-1.5" long
Ref. Abbott, 1974 p 420 bw

valvulus P. P. Carpenter, 1864
(3-3-2-0-3-2-0-1-2-4-0-0-0)
Pacific Awning Clam
Size 0.75" long
Ref. Abbott, 1974 p 420

velum T. Say, 1822
(3-3-2-0-3-2-0-1-2-5-0-0-0)
Common Atlantic Awning Clam
Size 0.5"-1" long
Ref. Abbott, 1974 p 420 bw