THE MAMMALIA OF THE DEEP EIVER BEDS. 87 



Measurements. 



M. 



Upper molar-prernolar series, length 117 



Upper premolar series, length 068 



Upper first premolar, length 014 



Upper first premolar, width 009 



Upper second premolar, length 022 



Upper second premolar, width 019 



Upper third premolar, length 019 



Upper third premolar, width 020 



Upper fourth premolar, length 019 



Upper fourth premolar, width 020 



Upper molar series, length 049 



Upper first molar, length 018 



Upper first molar, width 020 



Upper second molar, length 016 



Upper second molar, width 018 



Upper third molar, length ? .014 



Upper third molar, width ? .017 



Lower molar-premolar series, length ? .119 



Lower premolar series, length ? .066 



Lower second premolar, length 019 



Lower second premolar, width 003 



Lower third premolar, length 0185 



Lower third premolar, width 010 



Lower fourth premolar, length .017 



Lower fourth premolar, width 011 



Lower molar series, length 053 



Lower first molar, length 018 



Lower first molar, width 010 



Lower second molar, length '. 016 



Lower second molar, width 009 



Lower third molar, length 018 



Lower third molar, width 007 



Depth of mandible below m. 1 ? .032 



Depth of mandible below m. 3 047 



Height of condyle 103 



Breadth of angle to m. 3 068 



The horizontal ramus of the mandible is, for the most part, slender and shallow, 

 especially towards the symphysis ; but as the inferior border is nearly straight, and 

 the line of molars rises rapidly posteriorly, the jaw becomes quite deep beneath m. s. 

 The ascending ramus is high and the condyle is placed much above the level of the 

 molars. The angle is rounded and not prominent. The anterior border of the 

 ascending ramus is almost straight, broad and slightly grooved, the linea obliqua 

 externa being better developed than in the horse, but less so than in the more ancient 

 genera. My attention was called to this interesting transitional character by my 



A. P. S. — VOL. XVIII. L. 



