The Collaborative International Dictionary of English v.0.48:

Ichthyopsida \Ich`thy*op"si*da\, n. pl. [NL., fr. Gr. 'ichqy`s,
   -y`os, a fish + ? appearance.] (Zool.)
   A grand division of the Vertebrata, including the Amphibia
   and Fishes.
   [1913 Webster]