

1877.] ^-L*' [Cope. 



Descriptions of New Vertebrate from the Upper Tertiary Formations of the 



West. 



By E. D. Cope. 

 (Bead before the American Philosophical Society, December 21, 1877.) 



PlTHECISTES BREYIFACIES geil. et Spec. 110 V. 



Char. gen. These are chiefly known from a mandible which supports the 

 dentition of one side and part of the other. The dental formula is' I. 1 ; 

 C. 1 ; Pm. 3 ; M. 3. The single incisor of each side is weak and easily lost, 

 and there is on one side only, a small alveolus for a minute second incisor. 

 It is therefore probable that in some individuals the incisive formula is 2. 

 The canine is not large, and closes in front of the superior canine in the 

 usual manner. The first and second premolars are one-rooted, and their 

 crowns are wider than long. That of the third premolar is robust, but 

 longer. The molars increase rapidly in size, and are not prismatic, but 

 are well rooted. They are worn in the specimen, but their structure is 

 probably shallow selenodont. The last molar has a long heel or fifth lobe. 

 Char, specif. The mandibular ramus is very deep posteriorly, and the 

 incisive border is not prominent. The canine tooth is quite small, its trans- 

 verse diameter being less than that of the first premolar, and equaling it 

 antero-posteriorly. The exterior incisor is weak, and the crown expanded 

 transversely, and obtuse. The crown of the first premolar is worn deeply 

 by the superior canine. The transverse diameter at tlie base of the crown 

 exceeds the antero -posterior. The crown of the second is wider than long, 

 and of the third longer than wide. The molars increase rapidly in size 

 posteriorly, so that the length of the third equals that of the three premolars 

 plus the canine. The heel is long, and is connected with the remainder 

 of the crown by a narrow plate, or in section, an isthmus. There are no 

 cingula, but an accumulation at the bases of some of the teeth resembles 

 the deposit of "tartar." The symplysis is very robust, and its upper sur- 

 face is marked on each side by a low longitudinal swelling. The opposite 

 premolar series are slightly convergent. 



The form of the mandible of this animal, as well as the number and pro- 

 portions of the teeth, curiously resemble that of the corresponding part of a 

 monkey. The species was about the size of a red fox. 



Measurements. M. 



Length of ramus from heel of molar III 057 



" molar series 048 



" premolar series 015 



" second true molar 010 



Width " " 007 



Length of last molar 018 



Width of " at front 007 



Length of symphysis in front 020 



Depth of ramus at first premolar 017 



second true molar * 025 



