ON THE 



EXTINCT MAMMALIA OF DAKOTA AND NEBRASKA, 



INCLUDING AN ACCOUNT OF SOME ALLIED FORMS FROM OTHER LOCALITIES. 



By Prof. Joseph Leidt, 



INTRODUCTORY REMARKS. 



As indicated in the leading title of the present work, the succeeding pages mainly consist of 

 descriptions of the remains of extinct mammals obtained from the tertiary deposits of the piresent 

 States of Nebraska and Dakota, formerly comprised together in the territory of Nebraska. An 

 account is also given of a few additional remains of allied forms and of cotemporary age, discovered in 

 the States of Texas and California. The fauna to which all the remains belong apparently pertains to 

 the middle and later tertiary periods, extending perhaps from the end of the eocene or the beginning of 

 the mioeene, and throughout this continuously and through the pliocene. The geology of the region 

 related with the fauna in Nebraska and Dakota has been investigated by my colleague, Prof. Hayden, 

 and forms the subject of the introduction prepared by him for the work. 



The great occidental tertiary fauna of which we speak appears to be entirely distinct in character 

 from that of the more recent or post-pliocene period, to which belong most of the mammalian remains 

 hitherto described by authors from various parts of the North American continent. It is remarkable, 

 from its bearing a nearer resemblance and relationship to the faunaj of corresponding age, and to those 

 more recent, of the so-called old world, than it does to the post-pliocene and recent faunte of the two 

 Americas. 



In comparing the various faunre indicated, it would appear that in the evolution of mammalian life 

 the. mioeene and pliocene faunaj of North America had proceeded from Asia, but subsequently in a 

 great measure became extinct, while the post-pliocene and recent faunae may partly have succeeded 

 from the former, but mainly proceeded from South America and north-eastern Asia. 



The tertiary deposits of the Mauvaises Terres of the Makisi-ta Wapka, or White River, of Dakota, 

 are remarkable for the great quantity of fossil remains of mammals and turtles they have yielded 

 without further exploration than picking them up from the surface of the country. Detached from the 

 neighboring soft and readily disintegrating rocks, the fossils lie strewn about, and have often attracted 

 the attention of the least curious of those who have traversed the district. The stone heads and turtles 

 have even excited the wonder of the Indian. Most of the loose fossils have been gradually collected by 

 travellers and others, so that few of a conspicuous character, I am told, now remain. Of those 

 collected, by far the greater part have been submitted to my investigation, and these have amounted to 

 the enormous quantity of between three and four tons in weight. 



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