The Collaborative International Dictionary
Megastome
Megastome \Meg"a*stome\, n. [Gr. me`gas great + sto`ma mouth.] (Zo["o]l.) One of a group of univalve shells, having a large aperture or mouth.
Wiktionary
megastome
n. (context zoology English) One of a group of univalve shells, having a large aperture or mouth.