The Collaborative International Dictionary of English v.0.48:

Hippurite \Hip"pu*rite\, n. [Gr. ? decked with a horse's tail;
   "i`ppos horse + ? 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]