a genus of reptile of the family of land tortoises. There is one species, polyphemus. The genus is distinguished by a low flattened shell and short, broad claws on the front legs. The shell may be up to 34 cm long. G. polyphemus is found in the United States and northern Mexico. It digs deep burrows up to 12 m long. Adult specimens often live in pairs, feeding on plant life and less frequently on insects. From April to June the female lays four to seven spherical eggs.
The meat of the G. polyphemus is used as food; consequently its hunting is legally restricted in places.