300 STKOPSIS OF THE VERTEBRATE FAUNA OF THE PUERCO SERIES. 



pialia Multitubereulata, a suboi-der whidh commenced in the Triassic age, and which 

 terminated its existence so far as the ISTorthern hemisphere is concerned with the 

 end of the Puerco epoch. This series of animals gives a Mesozoic character to the 

 fauna, which is not necessarily counterbalanced by the characters of the remaining 

 types. The placentals are in all probability those which existed during the latter 

 part of Mesozoic time, and the absence of some of the forms of the Eocene increases 

 the weight of the impression thus produced. Thus two orders universally present 

 in the Eocenes, the Perissodactyla and the Rodentia, are wanting from the Puerco. 



In conclusion it may be safely asserted that in the Puerco fauna we find the 

 ancestors of the species of Eocene and of later times. In the Tajniodonta we get 

 ancestors of Tillodonta and probably of Rodentia and Edentata. In Creodonta we 

 get the ancestors of the Carnivora, in the flxmily of the Miacidse. In the Condylar- 

 thra we get the ancestors of the Diplarthra and Amblypoda, and in the Puerco Ara- 

 blypoda the ancestors of those of the following epochs. Hence the investigation of 

 this fauna possesses an especial interest for the mammalogist and for the evolutionist, 

 as well as for the geologist proper. 



I give first a list of the species, and then give descriptions of new species, with 

 the osteology of such as the material permits. 



In describing the dentition I have, after consultation with ray friend Professor 

 W. B. Scott, of Princeton, followed the method of enumeration of premolar teeth 

 inti-oduced by Kowalevsky, and adopted b}^ Schlosser. In this method the premolar 

 teeth are counted from behind forwards, so that the one usually enumerated as num- 

 ber four becomes number one, and vice versa. 



The only catalogue of the Vertebrata of the Puerco which has appeared was 

 published in the Proceedings of the American Philosophical Society for 1882, begin- 

 ning at page 461. Since that time the following publications relating to that fauna 

 have appeared : 



First Addition to the Fauna of the Puerco Eocene. By E. D. Cope, loc. cit., 1883, Jan., p. 545. 



Second Addition to the Knowledge of the Fauna of the Puerco Epoch, loc. cit., 1883, Dec, p. 309. 



On Some Fossils of the Puerco Formation. Proc. Acad. Nat. Sci. Phila., 1883, p. 168. 



Tlie Tertiary Vertebrata of the West. Report U. S. Geol. Surv. Terrs., P. V. Ilayden, Vol. Ill, Feb., 1885. 



On Some New T:cniodonta of the Puerco. Amcr. Naturalist, 1887, p. 469. 



The Marsupial Genus Chirox, loc. cit., 1887, p. r)G6. 



The present enumeration brings together all the species hitherto described, and 

 adds a number of ncAV ones. The whole number, it will lie observed, reaches 106, 

 which are referred to thirty-four genera. 



Information at present available indicates that there is some faunal difference 



