Source : Webster's Revised Unabridged Dictionary (1913)

Potamian \Po*ta"mi*an\, n. [Gr. ? river.] (Zo["o]l.)
   A river tortoise; one of a group of tortoises ({Potamites},
   or {Trionychoidea}) having a soft shell, webbed feet, and a
   sharp beak. See {Trionyx}.

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