In previous papers reasons have been given for dividing the Proboscidea into four main superfamilies, as follows:
I. Mœritherioidea, typified by Mœritherium, Oligocene, North Africa.
II. Dinotherioidea, typified by Dinotherium, Miocene and Pliocene, Eurasia.
III. Mastodontoidea, typified by the bunomastodonts and the mastodonts, Africa, Eurasia, North and South America.
IV. Elephantoidea, typified by the stegodonts, loxodonts, elephants, and mammoths, Africa, Eurasia, North America.
As clearly pointed out in the second paper on this subject (Osborn, 1921. 514, pages 2–5), these four superfamilies are clearly distinguished from each other by profound differences in the adaptations of the cutting teeth, namely, the first and second pairs of superior and inferior incisors characteristic of all Proboscidea. The author is not prepared at present to add to what has been said in previous papers regarding the mœritheres and dinotheres.
Continued observation of the types on which the species in all parts of . . .