90 Annals of the Carnegie Museum. 



" As previously stated, the discovery of a complete skull of Mery- 

 cochoerus shows that those previously described under that name must 

 be divided into two genera, though at present the generic limits cannot 

 be definitely defined. I include provisionally under the genus Mery- 

 cochcerus, of which M. proprins is the type, M. rusticus, M. laticeps, 

 M. madison/us, M. elrodi, and perhaps M. compress/dens and M. 

 obliquidens. Were the skulls of all these found, the genus might 

 have to be divided again." 



In this paper Promerycoc/uvnts was proposed provisionally for the 

 other species which had been included in the genus Meryeoehosrus, call- 

 ing them Promerycochoerus superbus, leidyi, etc. 



" Between these two groups as I have divided them there is an easily 

 recognizable difference in the inferior dentition. In P. montanus and 

 macros/egus, and, judging by the upper dentition in P. superbus and 

 ■ehe/ydra, the length of the premolar series nearly or quite equals that 

 of the molar series. . . . In Merycochoerus proprius, rus/icus, /a/ieeps, 

 compress/dens, a ///ramus, and mad/son/us, the premolar series equals or is 

 slightly less than the length of the first two molars and the anterior 

 lobe of iVLg. In the first species it is a trifle more, and they decrease 

 in about the order mentioned. . . . 



"In all of these there is more or less crowding of the first three 

 premolars, and Pj is placed obliquely in the jaw. In other respects 

 the mandibles vary so much that we may expect that further discover- 

 ies will show that they do not all belong to the same genus." 



In 1898, forty years after the type oi Me rye o charms was described 

 by Dr. Leidy, an expedition from the American Museum of Natural 

 History in charge of Dr. W. D. Matthew, secured, among other 

 extremely interesting fossils, almost complete skulls and skeletons of 

 Merycoc/iceri. This was an interesting discovery and it showed that 

 widely divergent lines had been included in the same genus. These 

 fossils were described by Dr. Matthew in his splendid memoir, Pass// 

 Mammals of /he Ter/iary of Co/orado. n While there may be a little 

 doubt that the one described as Merycochcerus propr/us should be in- 

 cluded in the same species as the one described by Leidy, yet there 

 appears to be little doubt that we have here the true Merycochocrus. 



Dr. Matthew describes, from higher beds, other similar fossils which 

 he thinks may belong to a different genus. 



Jl Memoirs Amer. Mm. of Nat. Hist., Vol. I., part VII. 



