(Science: zoology) A genus of fresh water or river turtles which have the shell imperfectly developed and covered with a soft leathery skin. They are noted for their agility and rapacity.
Synonym: soft tortoise, soft-shell tortoise, and mud turtle.
The common American species (Trionyx, or Aspidonectus, ferox) becomes over a foot in length and is very voracious. Similar species are found in asia and Africa.
Origin: NL, fr. Gr. (see Tri-) _ a claw.