The Extinct Mammalian Fauna of Dakota and Nebraska; together with a Synopsis of the Mammalian Remains of North America

Abstract

II.

IN the preceding article the Miocene portion of Dr. Leidy's great work has been reviewed. That part of it relating to the Pliocene and the Quaternary still remains for analysis. That we are able to classify the American Mammalia as the Miocene, Pliocene, and Quaternary, we owe to Dr. Leidy; and his definitions of the two former of these are amply supported by the results arrived at by the Geological Survey of the district, under the direction of Dr. Hayden. The Pliocene strata on the Niobrara River, and in the valleys of the Platte and Loup Fork Rivers, rest on the Miocene beds, which furnished the Mammalia treated of in the first essay. And thus there is evidence that the one series is of later age than the other. Patæontologically, also there is a most remarkable break Not one species and only one or two genera, namely, Rhinoceros and Castor (Aceratherium?), are common to the two. With this exception, all the Miocene Mammalia had disappeared during the time that intervened between the formation of the two lacustrine deposits in that region. This fact implies that the one formation is separated from the other by a shorter interval than their European analogues; for in the latter many genera, such as the Mastodon, Hip-parion, Hyaena, Elephant, and others, pass from Miocene into Pliocene in such a way as to cause one group of life gradually to shade off into the other, and to render it sometimes impossible to define the last stage of the one from the first of the other.

The Extinct Mammalian Fauna of Dakota and Nebraska; together with a Synopsis of the Mammalian Remains of North America.

By Dr. Leidy. With an Introduction on the Geology of the Tertiary Formations of Dakota and Nebraska; with a map. By Dr. Hayden. (Philadelphia, 1869. London: Trübner and Co.)