What is "mactra stultorum"

Mactra \Mac"tra\, n. [NL., fr. Gr. ? kneading trough, fr. ? to knead.] (Zo["o]l.) Any marine bivalve shell of the genus Mactra, and allied genera. Many species are known. Some of them are used as food, as Mactra stultorum, of Europe. See Surf clam, under Surf.

Mactra stultorum, previously sometimes known as Mactra corallina, is a species of edible saltwater clam, a marine bivalve mollusc in the family Mactridae, the trough shells.