II F. O shorn — Mammalia in North America. 459 



still more remarkable likeness to the Cats is exhibited in the 

 Palteonictis family, which, unlike the Hyaanodons, forms its 

 sectorials out of exactly the same teeth as the true cats. The 

 first American Palteonictis was found two years ago by Wort- 

 man, and this author and myself have suggested that this may 

 be the long-sought ancestor of the Felidaa. The Civets are 

 anticipated in the Proviverridae ; yet both Cope and Scott, the 

 highest authorities on this subject, believe that the dog-like 

 Miacidae alone formed the connecting link between the Creo- 

 donta and the true Carnivora. 



The foot structure of the ancient Puerco ungulates is still 

 only partly known. Cope has divided these animals into the 

 Amblypoda and Condylarthra. The Amblypoda are repre- 

 sented in the Puerco by a large form called Pantolambda, with 

 selenodont triangular upper molars, and possibly by Perip- 

 tychus, with bunodont triangular molars. The Pantolambda 

 molars were, as Cope has shown, converted into those of Cory- 

 phodon, the great lophodont Amblypod of the Wahsatch, by a 

 process exactly analogous to that in which the anterior half of 

 a Palaeotherium molar was formed, that is, they acquired outer 

 and anterior crests but no posterior crests. This Corypho- 

 don molar type was still later converted into the Ilintatherium 

 type by swinging around the outer crest into a transverse crest. 

 I have recently made a careful study of the fore and hind feet 

 of Coryphodon, and have found that while the fore foot was 

 subdigitigrade like that of the elephant, the hind foot was fully 

 plantigrade, the entire sole resting upon the ground. The 

 relation or connection between the Bridger Dinocerata and 

 these earlier Amblypoda is still unknown. The Puerco Perip- 

 tychus left no descendants. The other ungulates of the Puerco 

 were the Condylarthra, including the primitive Phenacodon- 

 tidse, the supposed ancestors of the Artiodactyls and Perisso- 

 dactyls. Much remains to be done to clear xip their relation- 

 ships. 



Succession of the Perissodactyls. 



In the Wahsatch and Wind River we find not only the last 

 of the Phenacodonts and Coryphodonts and the first of the 

 Dinocerata, but the first of the true Artiodactyls and Perisso- 

 dactyls. Recent studies of Cope, Schlosser, Pavlow, Filhol 

 have been directed to the phylogeny of the Perissodactyls with 

 very different conclusions. I agree most closely with Schlosser, 

 and have endeavored to show that the molar teeth give us a 

 key to their natural arrangement as shown in this column. 



