62 Annals of the Carnegie Museum. 



and a light posterior cingulum. Premolars three and four are quite 

 molariform. The jaw is long and slender, the symphysis well coossi- 

 fied, and there is a deeply emarginated diastema between the third in- 

 cisor and Py. The dental series is well separated from the base of the 

 coronoid process. The latter is thin transversely and broad antero- 

 posteriorly, and has superiorly a gentle backward slope. The con- 

 dyle is peculiar in having a broad and flat articular surface, not con- 

 vex as is usual in mammals. The mandible is much constricted in 

 front- of Py. The mental foramina are large. 



Chalicotherium bilobatum was established by Cope 26 on a mandib- 

 ular symphysis and part of the left ramus of an adult animal from the 

 Tertiary on Swift Current Creek in Canada. Cope states that " all 

 the premolars [are] two-rooted, showing that they are but three in 

 number'" ; this agrees with the specimen here described. Cope states 

 further that the canines and incisors are wanting in the Canadian 

 specimen. The " minute traces of alveoli of a canine and two in- 

 cisors on each side, which were probably present in the foetus" is of 

 strong specific, if not generic importance, The type of C. bilobatum 

 appears, from Cope's description, to be too imperfect for correct 

 comparison and may result in placing it in the genus Moropus, when 

 more complete material is found. 



Measurements. 



mm. 



Greatest length of mandible , 430 



Distance from 1 3 to P^ 53 



Distance from P ¥ to and including P^ 68 



Distance from P ¥ to and including M f ..' 119 



Antero-posterior diameter of P2 17 



Transverse diameter of P2 II 



Antero posterior diameter of P^ 23 



Transverse diameter of P3 15 



Antero-posterior diameter of P ¥ ... 28 



Transverse diameter of P T 19 



Antero-posterior diameter of M T 32 



Transverse diameter of M T 19 



Antero-posterior diameter of Mj 40 



Transverse diameter of M% 22 



Antero-posterior diameter of Mj 44 



Transverse diameter of M ¥ 22 



Vertical diameter of mandible at M^ 70 



Vertical diameter of mandible at P^ 5 2 



**Am. Naturalist, Vol. XXIII., pp. 151-155, 1889. 



