REFERENCES TO THE PLATES. 459 



Fig. 12. Outer view. Fig. 13. Inner view. 

 Fig. 14. View of the triturating surfaces of the molars. 

 Figs. 15, 16. Merychyus major. See page 121. 



Fragment of the right side of the upper jaw, containing the third and fourth premolars and the first 

 and second true molars. 

 Fig. 15. Outer view. Fig. 16. Triturating surfaces of the teeth. 



PLATE XII. 



All the figures are of the natural size. 



Figs. 1-5. Leptauchenia major. See page 124. 



Fig. 1. Upper view of the right side of a much mutilated skull. 



Fig. 2. Greater portion of the left ramus of the lower jaw, containing a complete series of teeth, from 

 the same specimen as the former. 



Fig. 3. View of the triturating surfaces of the molars of the series just mentioned. 



Fig. 4. Left upper jaw, from another individual, containing a complete series of molars and the 

 canine tooth. 



Fig. 5. View of the triturating surfaces of the same teeth. 



Figs. 6-20. Leptauchenia decora. See page 127. 



Fig. 6. Left side of a much mutilated skull. 



Fig. 7. Posterior fragment of the right maxilla, containing the last pair of molars. 



Fig. 8. Inferior view of the same specimen. 



Fig. 9. Anterior fragment of the right maxilla, apparently fi'om the same individual as the former, 

 containing the premolars except the first one. 



Fig. 10. Inferior view of the same specimen. 



Fig. 11. Fragment of a left upper maxilla, containing the last premolar and the true molars. 



Fig. 12. View of the triturating surfaces of the same teeth. 



Fig. 13. Fragment of the[_left side of a lower jaw, containing the last two molars. 



Fig. 14. Triturating surfaces of the same teeth. 



Figs. 1-5-17. Views of the outer, inner and triturating surfaces of a second true molar of the right 

 side of the lower jaw. 



Figs. 18-20. Similar views of a more worn tooth. 



Figs. 21, 22. Leptauchenia nitida. See page 129. 



Fig. 21. View of the remains of the right side of a skull imbedded in matrix. The outline of the 

 posterior portion of the lower jaw is preserved upon the matrix. 



Fig. 22. Upper view of the left side of the same skull, partially restored, from the opposite side. 



PLATE XIII. 



All the figures are of the natural size. 



Figs. 1-3. Agriochcerus latifrons. See page 135. 



Fig. 1. View of the left side of an almost complete skull, from the Mauvaises Terres of White River, 

 Dakota. Discovered by Dr. Hayden during his expedition in the summer of 1866. 



Fig. 2. View of the triturating surfaces of the upper molars, from the same specimen. 



Fig. 3. View of the triturating surfaces of the lower molars, likewise from the same specimen. 



Fig. 4. View of the triturating surfaces of the second and third or last lower premolars of Agrioclue- 

 rus antlquus, represented for comparison with the corrcspouding teeth of Fig. 3. 



