Elephant-like mammals both living and extinct are classed together in a single order bearing the name Proboscidea. Living members of the group are the elephants, of which the large Indian and African species are best known. Among prehistoric representatives the most frequently mentioned in the popular literature of North American animals are the following: The American Mastodon, an immigrant from Siberia which ranged over nearly all of the United States and Canada. It was principally a forest dweller, rarely found in plains regions, was abundant during the Pleistocene period and may have been known to the early American Indians; The Woolly Mammoth, which was about nine feet tall. It ranged over British Columbia into the United States and across to the Atlantic, disappearing in late Pleistocene time; The Columbian Mammoth, about eleven feet tall, lived in the early half of the Pleistocene period, ranging over the warmer portions of North America, including practically all of the United States and much of Mexico; The Imperial Mammoth, reaching a height of more than thirteen feet, and becoming extinct in the Middle Pleistocene. It was a western form, remains being found from Nebraska to Mexico City. Originally placed in the genus _Elephas_, the mammoths are referred to commonly as elephants, though technically they should not be regarded as such. Recent explorations and researches have added greatly to our knowledge of these animals but have also caused much confusion with regard to scientific names, for many new subdivisions of the larger group are now recognized, and it has become necessary to change some of the older nomenclature. [Illustration: A Long-Jawed Mastodont (_Trilophodon phippsi_). One of the Early American Proboscideans] The large mammoth exhibited by the Museum bears the impressive name of _Archidiskodon meridionalis nebrascensis_. Fifty years ago it might have been identified simply as a specimen of the imperial elephant and in such case would have received the old name of that species, which was _Elephas imperator_. But late in the last century it was proposed that the mammoths be recognized by some other name to distinguish them more sharply from living elephants. The name suggested for the new genus thus established was _Archidiskodon_, in recognition of the more archaic or primitive construction of the enamel plates in the mammoths molar teeth. The specific name, _meridionalis_, had been given to a kind of mammoth which is well known from the southern part of Europe, and the Latin name, signifying “southern,” had been applied to differentiate this species from the northern or woolly mammoth.