EXPLANATION OF PLATE VI. 



Figs. 1-9. Hyopsodus paulus. All of the natural size except Figs. 2, 5, 8, 9, which are magnified four 



diameters. * 

 Fig. 1. Right side of lower jaw, with the three molars. From an individual past maturity. 



Specimen from which the genus and species were first noticed. 

 Fig. 2. Triturating surfaces of the molars of the same specimen. 

 Fig. 3. Left side of lower jaw, with last premolar and the three molars. Specimen obtained 



by Dr. Corsou at Grizzly Buttes. 

 Fig. 4. Right side of lower jaw, with last premolar and the molars, but slightly worn. 



Specimen obtained by Dr. Carter. 

 Fig. 5. Triturating surfaces of the teeth from the same. 



Figs. 6, 7. Left side of two lower jaws containing the molars. From mature but compara- 

 tively young individuals. Dr. Carter. 

 Fig. 8. Series of the back two premolars and the molars of the right side. From a specimen 



loaned by Dr. Carter. 

 Fig. 9. First and second lower molars of the right side. From another specimen loaned by 



Dr. Carter. 



Figs. 10, 11. Microsus cuspidatus : 



Fig. 10. Portion of left side of lower jaw, with back two molars, natural size. Specimen 



from Black's Fork of Green River. 

 Fig. 11. Triturating surfaces of the two molars, magnified four diameters. 

 Fig. 12. Portion of right side of lower jaw, probably pertaining to the last-named animal. 



It contains the roots of the molars and the last premolar, the triturating surface of which 



is represented in Fig. 13, magnified four diameters. Specimen obtained by Dr. Carter near 



Fort Bridgor. 



Figs. 14-17. Microsyops gracilis: 



Fig. 14. Left; sido of lower jaw with the molars, natural size. Fig. 15. Triturating surfaces 



of the molars, magnified four diameters. Specimen obtained at Grizzly Buttes by Dr. 



Carter. 

 Fig. 1G. Loft sido of lower jaw, with the second molar and portions of the others, natural 



size. Fig. 17. The triturating surface of the second molar magnified four diameters. 



Specimen obtained by Dr. Carter at Grizzly Buttes. 



Figs. 18-22. Hyopsodus p.vuuts: 



Fig. 18. Right upper jaw, with throe premolars and the molars, magnified two diameters. 



Fig. 19. Triturating surfaces of the teeth magnified four diameters. Specimen obtained 

 by Dr. Carter at Grizzly Buttes, and apparently pertaining to the same individual as that 

 of Fig. 14. • 



Fig. 20. Triturating surfaces of the right upper molars, magnified four diameters, from a 

 second specimen. Dr. Carter. 



Fig. 21. Triturating surfaces of back two premolars and first molar of the left side, magni- 

 fied four diameters. Obtained by Dr. Carter at Lodge-polo trail. 



Fig. 22. Triturating surfaces of upper second and third premolars of right side, magnified 

 four diameters. Dr. Carter. 



Figs. 23-25. Paramys del:gatus : 



Fig. 23. Right sido of lower jaw, with all tho molars, natural size. Fig. 24. Triturating 



surfaces of the molars except the last, which is broken away excepting the outer portion, 



magnified three diameters. Grizzly Buttes. Dr. Carter. 

 Fig. 25. Triturating surfaces of the molar series, except tho last, of tho lower right side, 



magnified three diameters. From another specimen loaned by Dr. Carter. 



