F. B. Loomis — Ticholeptus Rusticus, etc. 281 



Aet. XX. — On Ticholeptus Rusticus and the Genera of 

 Oreodontidce; by F. B. Loomis. 



In 1858 Leidy established the genus Merycochoerus, 

 with M. proprius as the type species for Miocene oreo- 

 donts. Since that time the genus has been the one to which 

 every Miocene oreodont with inadequate data has been 

 referred, until the number of referred species became over 

 a dozen. It is not entirely unnatural to do this ; for the 

 dentition of oreodonts remains strikingly uniform, while 

 the shape of the skull and the character of the limbs 

 change remarkably. By 1901 it had become obvious that 

 more than one type of animal was included in the genus ; 

 and Douglass, using M. superbus as the type, gathered to- 

 gether a group of forms characterized by having heavy, 

 elongated skulls, with long nasals, wide heavy zygomatic 

 arches, a long heavy body and short stocky limbs, and es- 

 tablished the genus Pr ornery cochoerus with a half dozen 

 species to start with, to which have since been added as 

 many more. Very shortly after that Matthew published a 

 description of the skull and most of the skeleton of Mery- 

 cochoerus proprius, showing this to be a form with short- 

 ened nasals, a wide skull, and short limbs. This then es- 

 tablished the character of the forms which could be 

 referred to this genus and only one other was left in the 

 group, namely M. rusticus. 



It was the good fortune of the Amherst Expedition of 

 1919 to find in the Pawnee Creek Beds of N. E. Colorado 

 a very perfect skull of M. rusticus together with consider- 

 able quantities of skeletal material. These beds carry 

 only this one species of oreodont so there is very little dif- 

 ficulty in using all the skeletal material, though there was 

 associated with the skull considerable of the skeleton, 

 making the study of numerous other finds very easy. A 

 glance at the complete skull shows that it is not to be as- 

 sociated with M. proprius genericly ; but rather that it is 

 associated with forms described by Douglass under the 

 names Ticholeptus brachemelis and T. brericeps, though 

 at the same time specifically different. 



The type species of this genus is Ticholeptus zygomati- 

 cs Cope, which was figured by Scott in 1894 and by him 

 referred to the genus Merychyus. The specimen lacks 

 the nasal region and the feet, both parts much to be de- 



