Mastodon, a genus of fossil Proboscidea, closely related to the elephants, from which they differ only in their teeth. They had two incisors or tusks in the upper jaw, but slightly curved, and sometimes furnished with longitudinal bands of enamel on their surface. There were sometimes also a pair in the lower jaw. The molar teeth had fewer ridges than those of elephants, scarcely any cement between them, and conical cusps, whence the name (from the Greek mastos, "nipple"; odous, "tooth") is derived. Mastodon occurs in the Miocene and Pliocene rocks of the Old World, two species occurring in the English Crag; but in North America they survived into Pleistocene times. Their remains have been found in India, in the Andes, and perhaps in Australia.