Douglass — New Species of Merycochoerus in Montana. 75 



M. 



Fourth premolar, width* -0085 



First molar, length -0224 



First molar, width* -0126 



First molar, height -015 



Second molar, length *028 



Second molar, width *013 



Second molar, height -0245 



Third molar, length . -0446 



Third molar, width . -Oil 



Depth of ramus beneath pm2 -042 



Depth of ramus beneath pm 4, middle *053 



Depth of ramus beneath ml, middle *063 



Depth of ramus beneath m2, middle -076 



Depth of ramus beneath front part of m3 -098 



Depth of ramus beneath back part *125 



Found by the writer in layer of sand at bottom of Loup Fork 

 beds near top of White Kiver beds in bluffs on eastern side of 

 Lower Madison Valley about ten miles from Three Forks, 

 Gallatin Co., Montana. 



Merycochoerus madisonius n. sp. 



In my collection from the Madison bluffs is a lower jaw 

 fragment with the anterior lobe of m 3, m2, m i, the roots of 

 pms 4 and 3 and oi pm 1. It represents a somewhat older but 

 smaller animal than the one described as Merycochoerus laticeps, 

 from which it differs in several particulars. The correspond- 

 ing part of the ramus is much shorter. The anterior part has 

 about the same depth. There is not that sudden descent under 

 the interval separating m2 and m3, to form the rounded angle. 

 The foramen mentale is larger, narrower, and situated relatively 

 farther back, being mostly under prnJ^. The posterior part of 

 the symphysis is farther back, being beneath the interval 

 between pm 4^ and m 1. The ramus is much thicker near the 

 lower border under m 1, the two being in the proportion of 19 

 to 24. The lower border is preserved to a point beneath the 

 front lobe of m 3. Here it is much narrower than in M. 

 laticeps, being {■ the width. As nearly as I can determine the 

 length of the premolar series and the first two molars in the 

 present species is 8'8 cm ; in M. laticeps it is 10'3 cm . 



The length of the premolars and first two molars is about the 

 same as in M. rusticus. The foramen mentale is about the 



*The measurements of the width were taken at top of crown ; as, to preserve 

 the parts of the jaw in place, it was necessary to imbed it in plaster. 



Some teeth overlap a little, so measurements of individual teeth do not quite 

 coincide with the total. 



The measurements of depth of jaw are taken from upper projections of hone 

 between lobes of teeth. 



