PLATE XII. 



Spirifera davisi. 

 Fig. 1-4. Dorsal, front, ventral and profile view of a specimen. Page 112 



Spirifera divaricata. 



Fig. 5-11. A series of specimens showing variations in form and size. Page 113 



Spirifera duodenaria. 



Fig. 12, 13, 16. Ventral, dorsal and profile view of a specimen. Page 114 



Spirifera arctisegmenta. 



Fig. 14, 15. Ventral and dorsal view of a specimen. Page 108 



