EXPLANATION OF PLATE XVII. 



All the tigures of the natural size, except Figs. 9, 10. 



Fig. 1. Clupea humilis. From the original specimen obtained by Dr. John E. Evans, on Green River, 

 in 1856. 



Fig. 2. Clupea alta. From the " Petrified Fish Cut," on the Union Pacific Railroad, near Green River. 



Fig. 3. Petalodus aixeghaniensis. Tooth, front view, from a specimen obtained by Messrs. Meek and 

 Hayden, in the upper carboniferous formation of Fort Riley, Kansas. 



Figs. 4-6. Ciadodus occidentalis. Tooth found by Messrs. Meek and Hayden, in the upper coal 

 measures of Manhattan, Kansas. 

 Fig. 4. Back view. Fig. 5. Section of the crown. Fig. 6. Bottom of the root. 



Figs. 7, 8. Ptychodus occidentalis. Tooth discovered by Dr. John L. Le Conte, in the Cretaceous 

 formation east of Fort Hays, Kansas. 

 Fig. 7. Upper view. Fig. 8. Lateral view. 



Figs. 9, 10. Xiphactinus atjdax. A pectoral spine, one-half the natural size. 

 Fig. 9. Inferior view. Fig. 10. Superior view. 



Figs. 11-17. Mylocyprinus robustus. Pharyngeal bones, from Idaho, contained in the collection of 



Professor J. S. Newberry. 

 Fig. 11. Inferior view of a left pharyngeal, containing the three intermediate teeth. 

 Fig. 12. Inferior view of a right pharyngeal, containing the anterior three teeth. 

 Fig. 13. Same view of a smaller left pharyngeal, with the posterior four teeth. 

 Fig. 14. Similar view of another specimen, with the anterior three teeth and the bases of 



the posterior two teeth. 

 Fig. 15. Posterior view of a right pharyngeal of an old animal, with the second and fourth 



teeth. 

 Fig. 16. Inner view of a right pharyngeal, with the posterior four teeth. 

 Fig. 17. Posterior view of the same specimen. 



Figs. 18, 19. Oncobatis pentagonus. Dermal plate, from the Pliocene of Sinker Creek, Idaho. 

 Fig. 18. Upper view. Fig. 19. Lateral view. 



Fig. 20. Enchodtjs Shumardi. Dentary bone, natural size, but reversed in position. From the Cre- 

 ' taceous of Dakota. 



Figs. 21, 22. Cladocyclus occidentalis. Two scales, natural size. Found with the preceding. 



Figs. 23, 24. Phasgantodus dirus. From Cannonball River, Dakota. 

 Fig. 23. A tooth of the natural size. 

 Fig. 24. Dentary bone, reduced one-third. 



Fig. 25. Xystracanthus arcuatus. A dorsal spine, from Leavenworth, Kansas. 



Fig. 26. Hadrohyus supremus: 



The mutilated crown of an upper premolar tooth, natural size, seen on the triturating sur- 

 face. From the Miocene Tertiary of Oregon. 



