The Collaborative International Dictionary of English v.0.48:

Elasmobranchii \E*las`mo*bran"chi*i\, n. pl. [NL., fr. Gr. ? a
   metal plate + L. branchia a gill.] (Zo["o]l.)
   A subclass of fishes, comprising the sharks, the rays, and
   the Chim[ae]ra. The skeleton is mainly cartilaginous.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Elasmobranchii
    n 1: sharks; rays; dogfishes; skates [syn: Elasmobranchii,
         subclass Elasmobranchii, Selachii, subclass Selachii]