Tri·on·yx n. Zool. 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.
Note: ☞ The common American species (Trionyx ferox syn. Aspidonectus ferox) becomes over a foot in length and is very voracious. Similar species are found in Asia and Africa.
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