94 Annals of the Carnegie Museum. 



meryx, and others that indicate much more modernization than is 

 apparent in the typical White River." 18 



It is evident, then, that Dr. Matthew uses the " White River" as 

 the name of a formation which includes several beds belonging to 

 several different horizons. Its upper member according to the 

 usage of Dr. Matthew extends into the Miocene where it contains 

 genera and species, hardly separable from the Loup Fork immediately 

 overlying it, and these species are much more modernized than is 

 apparent in the typical White River. Merycochoerus, then, probably 

 is not a form belonging to the White River beds as these are com- 

 monly understood to be located in the geological series. So far as 

 my observation and study go Merycochoerus does not occur below the 

 Middle Miocene. With regard to Hayden's list in Leidy's " Extinct 

 Mammalian Fauna," there is not space to discuss it here, only to say 

 that few of the specimens enumerated in column " D" as contempo- 

 raneous with Merycochoerus proprius can be pointed to as definitely 

 marking horizons, when it is considered that in those early days of 

 discovery, fragments of jaws, etc., were very misleading. Then, too, 

 in collecting from deposits, which are undoubtedly in part of stream 

 origin, it would be strange if there were not some specimens put in 

 the wrong list. 



The typical Merycochoerus is probably older than the specimens 

 from Montana which, in part at least, have been wrongly put in that 

 genus. 



III. Prtmomotherium gen. nov. 



I propose this name for a new genus, the type of which is a nearly 

 complete skull with the mandible (Carnegie Museum Catalogue of 

 Vertebrate Fossils No. 796) formerly described as Merycochoerus laticeps 

 Douglass. 19 This specimen was very fully described in the paper cited. 

 I am now better able to give the characters which distinguish it from 

 the genus in which it was wrongly placed. 



Generic Characters. — Skull extremely short, brachy cephalic y 

 broad and low. Posterior poi'tion reduced in length more than the 

 anterior portion. Brain case small. Inclination of basi-cranial to 

 basi-facial axis extreme. Anterior narial opening of two portions, one 

 opening a little anterior to the orbits, the other a long slit between the 



18 " Fossil Mammals from Colorado," p. 372. See also pages 401 and 402. 



19 u New Species of Merycochoerus in Montana," Amer. four. Set., Vol. X., Dec, 

 1900, p. 428. 



