DAKOTA AND NEBRASKA. 155 



The last premolar, figure 7, c, has the same form as that of the latter anhnals in 

 the same condition of abrasion. 



The third premolar, figure 7, b, resembles that just mentioned, with its internal 

 lobe thinned and deeplj^ parted or notched in the middle. 



The second premolar, figure 7, a, in excess of the number in the Lama and Camel, 

 resembles the first of the former animal in the shape of its crown. This is laterally 

 compressed conical, and feebly trilobate. The tooth is inserted by a pair of robust 

 fangs. 



The measurements of the fossil, in comparison with those of the Camel, are as 

 follow : 



Breadth of face in advance of the premolars, 

 Breadth of face at the last molar alveoli. 

 Breadth of face at infra-orbital foramina, 

 Breadth of palate between last molars, 

 Breadth of palate between second premolars, 

 Length of closed series of upper molars, 

 Length of series of upper true molars, 



7. Two imjjerfect specimens of upper true molars probably belong to Procamelus 

 occidentalis. They are the second and last of the series, and are moderately worn. 

 Apparently they belonged to the same individual, and bear a near resemblance to 

 those of the Camel. The last molar measures 13 lines antero-posterierly at the outer 

 part of the triturating surface, aud 11 lines transversely at the base of the anterior 

 lobes. 



8. Two isolated incisors, from different individuals, — the first and second of the 

 series from the canine, — probably belong to this species. They closely resemble the 

 corresponding teeth of the Camel. 



Procamelus gracilis. 



Among the Niobrara fossils there are several isolated teeth and small fragments 

 of jaws with single teeth, which have been suspected to indicate a third species of 

 Procamelus, distinguished by the above name. 



One of the specimens, an isolated inferior last premolar, is represented in figure 15, 

 a, plate XIV. It resembles in form the corresponding tooth o£ Procamehcs robusiits 

 and P. occidentalis, but is much smaller. The worn triturating surface exhibits at its 

 back part an elliptical enamel pit, as that of the other species would at the same 

 stage of abrasion, and also as in the Camel and Lama. 



