The Collaborative International Dictionary of English v.0.48:

Trionychoidea \Tri*on`y*choi"de*a\, n. pl. [NL. See Trionyx,
   and -old.] (Zool.)
   A division of chelonians which comprises Trionyx and allied
   genera; -- called also Trionychoides, and Trionychina.
   [1913 Webster]