PLATE XIII. 



Rhynchonella tethys. 



Fig. 25-33. A series of specimens showing variations in size and num- 

 ber of plications. Page 83 



Spirifera segmenta. 



Fig. 36-38. Dorsal, ventral and profile view of specimen. Page 132 



Ryiichonella Carolina* 

 Fig. 1-3, 34, 35. A series of specimens showing variations in size. Page 75 



Gyrtina hamiltoniae. 



Fig. 4-12. A series of specimens showing variations in size and orna- 

 mentation. Page 90 



Cyrtina hamiltoniae, var. recta. 



Fig. 13. View of a small dorsal valve. Page 97 



Fig. 14. Ventral view of a specimen. 

 Fig. 15. Profile view of a specimen. 

 Fig. 16. View of a larger dorsal valve. 



Fentamerella arata. 



Fig. 17-20. Dorsal, ventral, front and profile view of a specimen. Page 49 



Cyrtina crassa. 

 Fig. 21-24. Ventral, cardinal, profile and dorsal view of a specimen. Page 95 



