82 Douglass — New Species of Merycochoerus in Montana. 



Species. Depth of ramus under 



Pm2 Pm3 Pm4 Ml M2 M3 



ant. pos. 

 M M M M M M M 



Merycochoerus laticeps -043 '053 -050 '053 -067 -076 -109 



M. altiramus '043 -054 -063 -078 -098 -125 



M. madisonius -052 -051 "055 '057 -061 



M. elrodi -062 -065 -90 



M. compressidens -050 -048 '045 -045 -044 -047 



M.? obliquidens? '032 -030 -027 -029 



In the above table the measurements are taken as nearly as 

 possible from the alveolar border at the middle of the last lobe 

 of the tooth, except under m.3 which is taken beneath the 

 anterior lobe, also the posterior one when present. 



.As previously stated, the discovery of a complete skull of 

 Merycochoerus 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 pro- 

 visionally under the genus Merycochoerus, of which M. 

 proprius is the type, M. rusticus, M. laticeps, M. madisonius, 

 M. elrodi, and perhaps M. compressidens, and M. obliquidens. 

 Were the skulls of all these found, the genus might have to be 

 divided again. The last two have a much slimmer ramus than 

 the others and M. compressidens has a first incisor. With 

 regard to M. obliquidens, which Cope does not mention in his 

 "Synopsis of the Oreodontidce," this is doubtful. 



I have no wish to supply a generic name for the other 

 species that have been included in this genus, as more experi- 

 enced workers will, I hope, soon make a thorough study of 

 all the data and material available. But for convenience I pro- 

 visionally call the other members Pr ornery cochoer us, as all 

 with the exception of Promerycochwrus montanus are older, 

 and some of the species are perhaps in the direct line of Mery- 

 cochcerus. Instead then of using the names Merycochoerus 

 superbus, leidyi, chelydra, macrostegus, and montanus, I will 

 use provisionally the terms Promerycochwrus superbus, leidyi, 

 chelydra, macrostegus and montanus respectively. 



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

 easily recognizable difference in the inferior dentition. In P. 

 montanus and macrostegus / and, judging by the upper den- 

 tition in P. superbus and chelydra, the length of the premolar 

 series nearly or quite equals that of the molar series. The 

 molar series may be somewhat longer in P. leidyi. In Mery- 

 cochoerus proprius, rusticus, laticeps, compressidens, altiramus, 

 and madisonius, the premolar series equals, or is slightly less 

 than the length of the first two molars and the anterior lobe of 

 m 3. In the first species it is a trifle more and they decrease in 



