p. 129-189, 23 p. of plates : ill., map. ; 27 cm.Includes bibliographical references (p. 185-189)."One. A large collection, mainly of isolated molars, from Águas do Araxá, Brazil, seems to represent a single population within a species identified as Haplomastodon waringi. The variation, described in some detail, is far greater than has hitherto usually been taken into consideration in the diagnosis of supposed species of mastodonts. 2. Mastodonts have been found at many localities scattered throughout Brazil. A few specimens are anomalous, but the great majority belong to, or are at least inseparable from, H. waringi on the basis of known characters. 3. Ecuadorian Haplomastodon is not at present specifically separable from H. waringi, and n...