n. [ Gr. &unr_; decked with a horse's tail; "i`ppos horse + &unr_; tail: cf. F. hippurite.] (Paleon.) A fossil bivalve mollusk of the genus Hippurites, of many species, having a conical, cup-shaped under valve, with a flattish upper valve or lid. Hippurites are found only in the Cretaceous rocks. [1913 Webster]