The maximum diameter of this almost circular shell is about 11 cm. Its outer covering, or periostracum, is thick, coarse and wrinkled in texture and brown or blackish in colour; so it is sometimes known as the black or mahogany clam. The name ocean quahog is accounted for by its general resemblance to the quahog and by the fact that it lives in fairly deep water (15 to 100 metres), in sandy mud. Its range is from Newfoundland to North Carolina. It may be found on beaches after an onshore gale, but has not been well known since it is inaccessible to the casual clam-gatherer. Now, however, large quantities of it are being landed in New England and the Middle Atlantic States, to be used for minced-clam products and stews. This is a result of a serious decline in the available stocks of surf clams.
