PALEONTOLOGY. 

 PLATE III. 



Page. 



PeNTACRINITES A8TEIU8CUS 345 



Figs. 1,2. Euhirged views of two of the disks, showing the extremes of variation of acute 

 ness in the angles of the star-like points. 



ASTERIAS T DUBIUM 344 



Fig. 3. View of a fragment from a larger block, showing three individuals, as obtained by 

 gutta-percha from the natural impression. 



LiNGULA BREVIROSTKA 346 



FiG-s. 4, .'>. Views of what appears to be a dorsal and a ventral valve, natural size. 



Ehynchonella mtrina '. 347 



Figs. (5,7. Views of two ventral valves, showing the extremes of variation in the number 

 of plications. 



OSTREA STRIGILECULA 348 



Fig. 8. View of the interior of an upper valvo of the ordinary form at the localities men- 

 tioned under the description. 



Fig. 9. Inferior of a small lower valve of the thin, flat variety. 



Fig. 10. A prolile of the same individual, sho^ving the slight elevation of the margin. 



Fig. 11. External or basal view of a larger deep valve, showing the scar of attachment. 



Fig. I'-i. Side view of another similar specimen, showing the great elevation of the margin 

 at the anterior border and below the cicatrix of attachment. 



GuypHjEa calceola var. nebrascensis 349 



Fig. 13. View of the interior of a specimen from the Big Horn Mountains, restored in front. 



lutroduccd for comparison. 

 Fig. 14. External view of the same specimen. . 

 Fig. 15. Profile view of the same. 

 Fig. 1(). Profile of another imperfect specimen, showing the striae of the surface. 



PSEUDOMOXOTIS (ELWIICROTIS) ORBICUUITA 356 



Fig. 17. View of the convex valve of the ordinary size. 



Fig. 18. View of a right valve, twice enlarged, showing the very small ear. 



Fig. 19. Enlargement of the surface striae from the specimen Fig. 19. 



Pseodomonotis (Eumicrotis) curta 354 



Fig. 20. View of a left valve of the ordinary form and size, enlarged to two diameters. 



Fio. 21. Enlarged view of the right side of a specimen, showing the characters of the 

 hinge Three diameters. 



Fig. 22. \ still further enlargement of the upper part of the shell, showing the generic fea- 

 tures of the shell. 



Fig. 23. Profile of the specimen, Fig. 21, enlarged to correspond. 



Fig. 24. Enlargement of the interior of a left valve. 



l^G. 25. Enlargement of the interior of a right valve, showing the character and construc- 

 tion of the ear-like fold in the shell. 



