Douglass — New Species of Merycochcerus in Montana. 77 



Measurements. 



Length of lower premolar series, estimated -049 



Length of ml ._ -018 



Width of m 1 ___ -0155 



Length of m 2 . _ -023 



Width of m 2 -0134 



Depth of jaw at lower border of symphysis -0585 



Depth of jaw under pm 4 -051 



Depth of jaw under m 1 middle 1 __ -055 



Depth of jaw under m 2 middle -057 



Depth of jaw under m 3 anterior lobe *061 



Length of foramen mentale '0096 



Width of foramen mentale __ _ ,. -0026 



Thickness of jaw under pm 4, greatest __ ._ -023 



Thickness of jaw under m 3, anterior part '0264 



Found by myself in the Loup Fork Lake beds, Madison 

 Valley, Montana. 



Upper Jaw. — From the same beds as the above is a fragment of 

 an upper jaw with the last three molars, which I refer provision- 

 ally to the same species. The part preserved differs from M. 

 laticeps in the more posterior position of the inferior border of 

 the anterior root of the zygomatic arch, the lowest part being 

 opposite the anterior part of m 1, while in M. laticeps it is oppo- 

 site the last lobe of m 2. In the present specimen the posterior 

 border of this root, which forms the anterior border of the 

 zygomatic foramen, is nearly vertical, while in the species above 

 named it slopes backward. The small, short, malo-maxillary ridge 

 extends forward horizontally, quickly dying out on the side of 

 the face above the posterior part of pm %. Above this the 

 surface as far as seen is flat and looks forward and upward. 

 Evidently the face contracted rapidly forward and upward, 

 but its exact shape cannot be told. This sudden contracting 

 would indicate a short skull to correspond with the shortening 

 of the jaw in the type above described. The outer border of 

 the palate next to the teeth is convex antero-posteriorly. The 

 species was smaller than M. laticeps. The wearing of the 

 teeth indicates a mature individual. There is a small posterior 

 lobe on the last upper molar as in M. proprius, but the median 

 external buttress extends more vertically outward. The other 

 columns were evidently prominent, though they have dis- 

 appeared. 



Measurements. 



Length of upper molar series ^ _ "072 



Length of m 1 _ '0183 



Width of m 1 '022 



Length of m 2 _ '0215 



Width of m 2 -021 



Length of m 3 -032 



Width of m 3 -0268 



