EXPLANATION OF PLATE V. 



All the figures of the natural size except Fig. 11, which is one- half the size. 



Figs. 1-3 Trogosus castoridexs. A lower jaw, discovered in the vicinity of Fort Bridger hy Dr. 



Carter. 

 Fig. 1.' View of the left ramus of the jaw. 

 Fig. 2. Triturating surface of the second true molar, much worn. The other molars are too 



much injured to be characteristic. 

 Fig. 3. Front view of the jaw, exhibiting the large rodent-like incisors. 



Figs. 4-11. Paxjeosyops pajludoscs : 



Fig. 4. An upper last premolar, the triturating surface much worn. From Henry's Fork. 

 Hayden's collection. 



Fig. 5. An upper last premolar, nearly unworn. This is one of the original specimens upon 

 which the genus and species were established. From Church Buttes. Hayden's collec- 

 tion of 1870. 



Fig. 6. Outer view of a last upper molar, left side. Henry's Fork. Hayden's collection 

 of 1870. 



Fig. 7. Triturating surface of the same specimen; the outer fore-part much fissured, with 

 the portions displaced and the single inner lobe partially broken away. 



Fig. 8. Outer view of a second upper molar, from the opposite side of the same individual. 



Fig. 9. The triturating surface, with the outer lobes much worn. Figs. 6-9 are from 

 specimens, which were attributed to the same species at the time of the original notice of 

 it in the Proceedings of the Academy of National Sciences, Philadelphia, 1870, p. 113. 



Fig. 10. View of the triturating surfaces of the last two premolars and the molars from the 

 specimen represented in the next figure. 



Fig. 11. Left ramus of a lower jaw, containing the teeth just indicated. This fine specimen 

 was discovered by Dr. Carter thirteen miles southeast of Fort Bridger. 



