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University of California Publications in Geology [Vol. 13 



were appressed very closely and bound together by a ligament, as in 

 modern otarids. 



Owing to the fact that a considerable portion of the inferior margin 

 is broken away, there is exposed the inferior dental canal for the 

 passage of the dental nerve which traverses the mandible below the 

 roots of the molar series ; this also corresponds very well in position 

 with that of Eumetopias. This canal is of large size in order to pro- 

 vide adequate nourishment for the heavy dental series. As a whole, 

 this lower jaw reveals a strong resemblance in its configuration and 

 proportions to that of Eumetopias, but differs in that the mandible 

 is much thinner. 



The mandible of this form resembles that of Alachtherium and 

 Prorosmarus in the possession of incisors I 5 and I 5 , a single canine, 

 and in the persistent separation of the opposite rami of the jaw at 

 the symphysis, but differs in being decidedly more robust, and in 

 the possession of an abrupt rounded chin in contrast with the sloping 

 chins of the former. The coronoid and the molariform series must 

 have been in approximately the same plane, but such was not the 

 case in either Prorosmarus' 2 or in Alachtherium as illustrated by the 

 figures of Van Beneden. 3 The molariform series are very closely 

 spaced as in Prorosmarus, though the true molars are wanting in 

 the latter. 



Though the crowns have been broken off of all the teeth with the 

 exception of the canine, the alveoli remain. From these it can be seen 

 that the dental formula was as follows : 



I. 2 (h, I3) ; C, T ; Pm, 4 (Pm r Pm 5 ) ; M, 2 (M T , M 5 ). 



Measurements 



Anteroposterior diameter of alveolus, first incisor 9. mm. 



Anteroposterior diameter of alveolus, second incisor 10.5 mm. 



Anteroposterior diameter of alveolus, canine 28.5 mm. 



Anteroposterior diameter of alveolus, first premolar 15. mm. 



Anteroposterior diameter of alveolus, second premolar .... 17. mm. 



Anteroposterior diameter of alveolus, third premolar 17.5 mm. 



Anteroposterior diameter of alveolus, fourth premolar .... 17.8 mm. 



Anteroposterior diameter of alveolus, first molar 17.8 mm. 



Anteroposterior diameter of alveolus, second molar 9.5 mm. 



Height of canine crown above ramus 56. mm. 



Depth of jaw below first premolar 67. mm. 



Extreme length of symphysis (estimated) 105. mm. 



- Berry, E. W., and Gregory, W. K., loc. tit., fig. 4a. 



3 Van Beneden, P. J., Description des ossements f ossiles des environs d 'Anvers, 

 Ann. Mus. Boy. Hist. Nat. de Belgique, atlas, vol. 1, pi. 1, fig. 2, Brussels, 1877. 



