‖Tri‐on″yx (?), n. [NL., fr. Gr. � (see Tri-) + � a claw.] (Zoöl.) 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. Called also soft tortoise, soft-shell tortoise, and mud turtle.
☞ The common American species (Trionyx, orAspidonectus, ferox) becomes over a foot in length and is very voracious. Similar species are found in Asia and Africa.