The Collaborative International Dictionary of English v.0.48:
Hyracotherium \Hyracotherium\ n. An extinct horse genus, formerly called genus Eohippus. Syn: genus Hyracotherium. [WordNet 1.5]WordNet (r) 3.0 (2006):
Hyracotherium n 1: extinct horse genus; formerly called eohippus [syn: Hyracotherium, genus Hyracotherium]