What is a river tortoise; one of a group of tortoises (Potamites, or Trionychoidea) having a soft shell, webbed feet, and a sharp beak. See Trionyx called?

potamian — A river tortoise; one of a group of tortoises (Potamites, or Trionychoidea) having a soft shell, webbed feet, and a sharp beak. See Trionyx. (Webster's 1913.)

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