Tertiary Vertebrata of the West. 413 



yielded the higher vertebrata. Of Batrachia, the only Tertiary 

 specimen known is from the Green Eiver beds, and belongs to a 

 tailless Batrachian, but too imperfect for description. 



The Keptilia of American Eocene age are in no way remarkable 

 except for the appearance of new genera. The Crocodilia differ in no 

 important character from existing species of the genus Crocodilus. 

 Five species are found in the Wasatch beds, and six other species in 

 the Bridger beds. Seven species are here described : one, G. heterodon, 

 is as small as an Iguana, while C. clavis is equal to the largest East 

 Indian species. The Testudinata are more numerous. Sixteen 

 species are found in the Wasatch beds and thirty-two in the Bridger 

 beds. Emys, Trionyx and Plastomenus are genera surviving from the 

 Cretaceous period, while six new genera appear, of which five are 

 limited to these deposits. The new genera include Axestus, which 

 belongs to theTrionychidas, Anostira of Leidy, Hadrianus, Notomorpha.. 

 The genus Emys is represented by eleven species. The Lacertilia 

 are known from three species of Champsosaurus, especially interesting 

 as a type which survives from the Cretaceous Laramie formation. 

 Only one Serpent is known ; it is referred to an extinct genus 

 Protagras. After the remarkable reptile fauna of the Laramie 

 and Cretaceous rocks, this reptile fauna may seem tame ; but any one 

 who studies the beautiful plates which illustrate it will find abundant 

 materials for philosophic study among the narrow-nosed Crocodilia, 

 the variously-modified Tortoises, and the vertebras of Champsosaurus* 



Turning to the Mammals, Professor Cope reminds us that the 

 Mammalia, like the Keptiles of the Permian epoch, have the family 

 types in the Eocene rocks of America all more generalized, and 

 that the orders are not so sharply differentiated from each other as 

 in the later periods of the earth's history. The contribution there- 

 from which America now furnishes to our knowledge of the Mam- 

 malia is one of the most interesting chapters in the history of the 

 group. 



The story begins with the Marsupialia. This is one of the most 

 difficult groups to define accurately on account of the strong insecti- 

 vorous strain of characteristics which is so often present among 

 fossils. But among genera which are more definite in their affinities 

 is the remarkable genus Catopsalis, a rodent-like type with the jaw 

 inflected as in the Kangaroo and Kangaroo Eat, but with a tuber 

 culated Mastodon-like molar dentition. Ptilodus is another interest- 

 ing Marsupial, remarkable as representing the Purbeck Plagiaulax 

 in the American Eocene, though the affinity is not of a distant kind. 



Passing to the Bodentia, the representatives are again few. They 

 are apparently allied to the Squirrels, and are referred to five species 

 of the genus Plesiarctomys, a well-known type in the Eocene of 

 France. 



The next order is termed Bunotheria. It is defined as having the 

 animals armed with claws, with a transverse mandibular condyle, the 

 molar teeth usually tubercular, and with incisors in the premaxillary 

 bone. There are usually five digits, and commonly a third trochanter 

 to the femur. It comprises all those animals which the author had 



