hy·ra·co·ther·i·um 
(hī′rə-kō-thîrē-əm)
(hī′rə-kō-thîrē-əm)n.
A small herbivorous equid of the genus Hyracotherium (syn. Eohippus) of the Eocene Epoch, having an arched back, relatively short neck, four-toed front feet, and three-toed hind feet.
[New Latin Hyracothērium, genus name : hyrax, hyrac-, hyrax (from certain shared skeletal characteristics); see HYRAX + Greek thērion, wild beast; see TREACLE.]