Size

Shell length: reaching 25cm (10") Shell width: reaching: 10cm (4")

Recognition Characters

Has 15-25 radiating ribs, upper ribs are large and usually bear many erect, hollow, and sometimes tubular spines. Abductor muscle scar on interior of shell reaches end of the nacreous layer.

Color

Dark, grayish brown

Habitat & Depth

Low tide line to 90'.

Distribution at GRNMS

Occasional. Bivalve remains only partially exposed above sediment with shell open. More common on soft sediments away from ledge.

Geographic Range

North Carolina south to Florida, Gulf of Mexico west to Texas and Brazil

Behavior & Notes

Atrina rigida and A. seminuda are very similar in morpholigical appearance. The two species are separated by the difference in the position of the posterior abductor muscle scar in the nacreous layer (the pearly interior region) of these bivalves. In A. rigida the scar reaches the edge or border of the nacreous layer while in A. seminuda the scar is completely enclosed within the nacreous layer.

Synonyms

References