33Jr M. R. Thorpe — A New Merycoidodon. 



Aet. XXVII. — A Neiv Merycoidodon; by Malcolm Ruth- 

 erford Thorpe. 



[Contributions from the Othniel Charles Marsh Publication Fund, Pea- 

 bodj Museum, Yale University, New Haven, Conn.] 



Introduction. 



It is clearly apparent that the generic name Mery- 

 coidodon has priority over those of Oreodon and Cotylops, 

 as pre^dously pointed out by Grilmore and Hay. Yet 

 Leidy preferred the name Oreodon, and this has been 

 nsed by nearly all subsequent writers. "When so great a 

 group has been universally designated by a certain name 

 for seventy years, and when this name is not a misnomer 

 with regard to classification, it seems that its retention 

 would be desirable, especially as both Oreodon and Mery- 

 coidodon were proposed by the same author. 



Merycoidodon culhertsonii (1848), Oreodon prisons 

 (1851), 0. rohiistus (1851), and Cotylops speciosa (1851) 

 are considered synonymous. The type of Merycoidodon 

 possessed partly deciduous and partly permanent teeth ; 

 that of Oreodon had all permanent dentition; while the 

 Cotylops t}^e had all deciduous. 0. prisons and 0. 

 rohnstus are the same. 



This genus embraces five species and one subspecies, as 

 now defined. They are all well marked and, with one 

 exception, limited to the Middle Oligocene, the exception 

 being M. affinis from the Lower Oligocene (Chadron). 

 The majority of these forms have been well described and 

 repetition willbe avoided as much as possible in this 

 paper. There are, however, a few factors which it is 

 interesting to bring out. 



Merycoidodon cnlhertsonii cidhertsonii was exceedingly 

 numerous, and must have roamed in droves. Of this one 

 species alone, there are represented at least 400 indivi- 

 duals in the Marsh Collection in this Museum. This is, 

 moreover, a very conservative estimate, as there are 

 skulls and parts of skulls and jaws of some 340 individ- 

 uals, together with a large quantity of skeletal parts 

 belonging to these and many more of the same form. 



This species was studied to some extent from a quan- 

 titative standpoint, and the determination of the relative 

 age of the individuals at death is given below. The com- 



