The Collaborative International Dictionary of English v.0.48:

Emydea \E*myd"e*a\, n. pl. [NL., fr. Emys a genus of tortoises,
   L. emys a kind of fresh-water tortoise, Gr. ?.] (Zo["o]l.)
   A group of chelonians which comprises many species of
   fresh-water tortoises and terrapins.
   [1913 Webster]