338 University of California Publications in Geology [Vol. 7 



The peculiarity of specimen 20052 may be accounted for on 

 the assumption that it is a "sport" or "monstrosity" of Mery- 

 codus necatus, a common form in the Mohave region. A large 



Fig. 4. Merycodus necatus Leidy. Outer side of horn. No. 19832, X 

 Mohave Beds, Mohave Desert, California. 



number of Merycodus horns have been found in the Mohave Beds, 

 but on no other specimen has there been noted any suggestion 

 of the form seen in no. 20052, so that there was no common 

 tendency to develop this type of horn. 



Specimen 20052 represents a type distinct from the other 

 available specimens of the Mohave fauna and, so far as the writer 

 is aware, it is the only known specimen. This may possibly be 

 urged against the view that it is an undescribed form, and not 

 a variation or a sport of a known Merycodus species. In this 

 connection it should be noted that the Mohave fauna is as yet 

 very imperfectly known, and that a considerable number of the 

 most important elements in the fauna have been represented by 

 single fragmentary specimens. For a considerable time the 

 oreodont group was known from the Mohave region only by a 

 fragment of a lower jaw with two imperfect teeth, this being 

 the only oreodont found in an area including all of California 

 and nearly all of Nevada. 



