PALEONTOLOGY. 

 PLATE III. 



Page. 

 PENTACRWITES ASTERISCUS 345 



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

 ness in the angles of the star-like points. 



ASTERIAS ? DTJBIUM 344 



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

 gutta-percha from the natural impression. 



LlNGULA BREVIROSTRA 346 



Figs. 4, 5. Views of what appears to be a dorsal and a ventral valve, natural size. 



Khynchonella myrina 347 



Figs. 6, 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 valve of the ordinary form at the localities men- 

 tioned under tbe description. 



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



Fig. 10. A profile of tbe same individual, showing tbe slight elevation of tbe margin. 



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



Fig. 12. Side view of another similar specimen, showing the great elevation of tbe margin 

 at tbe anterior border and below the cicatrix of attachment. 



Grypelea calceola var. nebrascexsis 349 



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



Introduced for comparison. 

 Fig. 14. External view of the same specimen. 

 Fig. 15. Profile view of the same. 

 Fig. 16. Profile of another imperfect specimen, showing the striae of the surface. 



PSEUDOMONOTIS (EUJIICROTIS) ORBICULATA 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. 



PSETJDOMONOTIS (EUMICROTIS) CURTA 354 



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



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

 binge Three diameters. 



Fig. 22. A 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. 



Fig. 25. Enlargement of the interior of a right valve, showing the character and construc- 

 tion of the ear-like fold in tbe shell, 



