340 GEOLOGICAL SURVEY OF THE TERRITORIES. 



IV.— REPORT ON THE VERTEBRATE FOSSILS OF 

 THE TERTIARY FORMATIONS OF THE WEST. 



By Prof. Joseph Leidy. 



In the present report the writer has simply given a brief notice of 

 the various vertebrated animals whose fossil remains have been collected 

 in the tertiary deposits of the West. For a full account of most of the 

 extinct mammals which are subjects of notice, the reader is referred to 

 the work entitled " The Extinct Mammalian Fauna of Dakota and Ne- 

 braska," published in the seventh volume of the Journal of the Academy 

 of Natural Sciences of Philadelphia. More or less full accounts of the 

 other animals, also the subjects of notice, are published in Owen's Geo- 

 logical Survey, the fifth volume of the Pacific Railroad Reports, the con- 

 tributions of the Smithsonian Institution, and the Proceedings of the 

 Academy of Natural Sciences of Philadelphia. 



The vertebrate fossils collected in Professor Hayden's last two expe- 

 ditions, though forming part of the material of the report, will be more 

 fully described and illustrated in an extended treatise in future. 



The short time allowed for the preparation of the report amid the 

 many duties of the writer, must serve as his apology for its imperfect 

 character. 



The tertiary formations of the North American continent west of the 

 Mississippi, so far as they have been explored, in the States and Terri- 

 tories of Kansas, Dakota, Nebraska, Wyoming, Colorado, Idaho, Cali- 

 fornia, and Oregon, have yielded a great quantity of remains of verte- 

 brated animals, indicating different races which existed in earlier ages, 

 and which have entirely passed away. The principal deposits from 

 which the greater number of fossil remains have been obtained are 

 those of the mauvaises terres of White River, Dakota, those of the 

 valley of the Niobrara River, Nebraska, and the Bridger Group of rocks, 

 near Fort Bridger, Wyoming. The deposits especially referred to ap- 

 pear to be all of fresh-water origin, and to have belonged to the middle 

 and later tertiary epochs. 



Most of the vertebrated remains submitted to the examination of the 

 author are part of the valuable fruits of the geological explorations of 

 Professor Hayden, either engaged in expeditions of others, or under his 

 own control. Many have been obtained in the explorations of Dr. 

 David Dale Owen, Dr. John Evans, Mr. F. B. Meek, Mr. Clarence King, 

 and others. 



By far the greater number of vertebrated remains are those of 

 mammals, though some of the same or cotemporaneous formations are 

 rich in the evidences of reptilian life, and likewise those of fishes. 



MAMMALIA. 



The mammalian remains of the western tertiary formations appear 

 mainly to belong to the miocene period, though many evidently pertain 

 to a later age than the others, and most likely belong to the pliocene 

 period. Perhaps also a few of the remains belong at least to the later 

 part of the eocene period, especially those found in the lowest strata of 

 the mauvaises terres of White River, Dakota, and those found in the 

 Bridger Group of tertiary rocks of Wyoming. 



The fossil remains of mammals thus far collected in the western 



