LOXOLOFHODON AND UINTA THERIUM. 



27 



Teeth — Upper Jaw. 

 01 ^ ^ 



Dental formula: /-, Pm—, The narrow premaxillaries are eden- 



3133 



tulous in all the known genera of the Dinocerata. Behind the maxillo-premax- 

 illary sutures are the strong recurved canines which form a striking feature of 

 these animals. These are not preserved in either of our skulls, although with 

 one of the lower jaws, figured in Plate III., Fig. i, the tip of a tusk was found 

 and has been figured in the same plate, Fig. 6. It is lanceolate in outline, with 

 a median ridge worn by friction with the pendent process of the lower jaw. 

 This belongs to Loxolophodon. Cope describes that of L. CoryitiUis as a tusk of 

 compressed form strongly recurved, and with anterior and posterior cutting 

 edges. According to Marsh, the tusk of Uintatherium {Dinoceras) mirabile has 

 a decidedly lance-shaped extremity. The Museum contains no remains of the 

 canines of Uintatherium. In this genus they were protected by the pendent 

 flange of the lower jaw, but projected widely below the short corresponding 

 processes in Loxolophodon. 



The molar series are peculiar for their small size in proportion to the skull. 



Upper Molar-Premolar Series. 



The upper molar-premolar series are poorly preserved in Loxolophodon, pre- 

 senting much-worn crowns and broken edges. They agree in essential charac- 

 ters, as far as can be judged from our specimens, with those of Uintatherium, a 

 description of which (Plate III., Fig. 5) follows. In the table of measurements 

 the difference in size is seen to be in keeping with the greater dimensions of the 

 Loxolophodon head, which is nearly a third larger. 



Premolars. The first premolar is not preserved in our specimen. The sec- 

 ond and third are subequal and of about the same conformation, implanted by 

 three fangs, one 'internal and two external. A large basal ridge completely sur- 

 rounds the sub-circular crown. The crown, somewhat trihedral above, is sur- 

 mounted by two transverse grinding edges ; of these, the anterior is the 

 lower and crescent shaped, while the posterior is straight. Together they 

 form an irregular V opening outwards. The anterior ridges throughout the 

 series are much the most worn. 



Molars. The true molars increase in size regularly backwards. The first, 

 worn almost to the basal ridge, is larger than the last premolar, and shows, more- 

 over, an accessory tubercle on the inner side of the posterior ridge. The 

 extremities of the ridges rise into points and their summits are transversely con- 

 cave. In the last molar there are but two fangs, which are long and wide, 



