468 REFERENCES TO THE PLATES. 



Fit's. 9 10. External oblique and upper views of the crown of an inferior premolar, apparently the 

 second, of the natural size. 



Fi^s. 11, 12. Similar views of an inferior premolar, apparently the first, of the natural size. 



PLATE XXV. 



Figs. 1, 2. Mastodon mirificus. See page 249. Figures one-half the diameter of nature. 

 Fig. 1. Outer view of the greater portion of the left side of the lower jaw, containing a single molar 

 tooth. 



Fig. 2. Upper view of the same specimen. 



Fig. 3. Elephas impeeatoe. See page 25.5. One-third the diameter. 



Fragment of a molar tooth, viewed on the triturating surface. 



PLATE XXVI. 



Figs. 1-6. IscHYROMYS TYPUS. See page .335. 



Figs. 1-3. The natural size. 



Fig. 1. Upper view of the skull. It exhibits the supra-occipital, part of the squamosals pierced at 

 their upper pa,Tt by a large foramen («), the frontals, the parietals, on each side of the latter the 

 alveolar border of the maxillaries, and in front part of the latter and the outline of the back ends of 

 the nasals. The frontal of the left side has been restored from the right of the specimen. 



Fig. 2. View of the right side of the same specimen, partially restored from the left side. 



Fig. 3. Right side of the lower jaw from a different individual. The specimen, of this figure, was 

 obtained from the Mauvaises Terres of White River; the specimen, of the preceding figures, was 

 derived from Bear Creek, a tributary of the Sheyenne River. 



Figs. 4-6. Three times the diameter of nature. 



Fig. 4. View of the triturating surfaces of the upper molars of the left side, from the same specimen 

 as Figs. 1, 2. They count from left to right. 



Fig. 5. View of the triturating surfaces of the lower molars of the left side, from a specimen 

 accompanying that of Fig. 3. 



Fig. 6. Similar view of the molars of the right side, from an older specimen than the preceding, 

 which it accompanied. 



Figs. 7-11. Pal^ocastor nebeascensis. See page 338. 



Figs. 7-9. Of the natural size. 



Fig. 7. Ujiper view of a much mutilated skull. Fig. 8. View of the right side of the same. 



Fig. 9. View of the left side of the lower jaw, from another specimen. 



Figs. 10, 11. Twice the diameter of nature. 



Fig. 10. View of the triturating surfaces of the upper molars of the right side. They count from 

 right to left. From a different specimen than the preceding. 



Fig. 11. View of the triturating surfaces of the lower molars of the right side. They count from 

 right to left. From a different specimen than the preceding. 



Figs. 12, 13. EuMYS elegans. See page 342. 



Fig. 12. View of the left side of the lower jaw, twice the diameter of nature. The outline is com- 

 pleted from the jaw of the Rat. 



Fig. 13. View of the triturating .surface of the tooth contained in the specimen of the preceding 

 figure, maguilicd fuur diameters. The tooth is the left inferior median molar. 



