REFERENCES TO THE PLATES. 461 



Figs. 12-14. Megalomeryx niobraeensis. See page 161. 



Fig. 12. A first or second lower true molar, moderately worn. 



Fig. 13. Triturating surface of the same tooth. 



Fig. 14. Triturating surface of a much worn first lower true molar. 



Fig. 15. Procamelus gracilis. See page 155. 



Triturating surfaces of three premolars of the left side. a. A last premolar, but probably a penulti- 

 mate of P. oceidentalis. h, c. Penultimate and antepenultimate premolars, from a difierent individual 

 than the preceding, and probably belonging to a species of the succeeding genus. 



Figs. 16, 17. HojiocAMELUS caninus. See page 158. 



Fig. 16. Fragment of the right maxilla, with the second and third premolars, d, e, viewed from 

 beneath. 



Fig. 17. Representation of a portion of the left upper jaw, reconstructed from fragments belonging 

 to the two sides, a, caniniform incisor ; h, canine tooth ; c, caniniform premolar ; d, e, second and third 

 premolars. 



PLATE XV. 



Figs. 1-4. Procamelus EOBUsxrs. See page 148. 



Fig. 1. Portion of the right ramus of the lower jaw, two-thirds the diameter of nature, a. Canini- 

 form or first premolar, the crown blunted by attrition; 6, second premolar, nearly unworn; c, third 

 premolar, partially restored from another sijecimen ; rf, last premolar; e, first true molar ;/, sockets 

 for the second true molar ; g, last true molar. 



Fig. 2. Teeth, from the same specimen as the preceding, seen on their triturating surfaces, of the 

 natural size, h, second premolar ; d, last premolar ; e, g, the first and last true molars. 



Fig. 3. Outer view of an upper true molar, probably the first of the right side, of the natural size. 



Fig. 4. View of the triturating surface of the same sjjecimen as the last. 



Figs. 5-7. Peocamelxjs occidentalis. See page 151. 



Fig. 5. Portion of the right side of the lower jaw, two-thirds the diameter of nature, a, first or cani- 

 niform premolar, ideally introduced ; h, c, the second and third premolars, introduced from other speci- 

 mens; (/, last premolar; e,f, g, true molars, parts of which are restored. 



Fig. 6. View of the triturating surfaces of the lower molar teeth, partly from the preceding sjiecimen 

 and partly from others, of the natural size, h, c, the second and third premolars, belonging to a differ- 

 ent specimen from the teeth behind ; d, last premolar, from the same specimen as fig. 5 ; e,/, g, true 

 molars from the same as the latter, partially restored. 



Fig. 7. Inferior view of the left side of a mutilated specimen of the upper jaw, of the natural size. 

 a, b, c, second, third and fourth premolars, restored from the teeth on both sides of the specimen. The 

 true molars are ideally restored in outline, a portion of the crown ouly of the first molar being retained 

 in the fossil. 



Figs. 8, 9. Peotomeryx Halli. See page 160. 



Fig. 8. Anterior portion of the left side of the lower jaw, of the natural size. 



and medilateral couTolulions are separated by a well-marked fissure, as in the Hog. In the cast the lamdoidal con- 

 volution is not Tery distinct from the material occupying the position of the interhemispheral fissure. The post- 

 sylvian convolution forms a well-marked lobe, separated from the anterior cerebral lobe. The cerebellar cast, viewed 

 above, appears nearly half the size of that of the cerebrum, but its bulk is actually hardly a third of that of the latter. 

 Its median or vermiform lobe projects above nearly as much as the cerebrum, and forms a prominent convex, semi- 

 circular ridge. The lateral lobes or hemispheres are small compared with the former. 



