PLATE X, 



Spirifera byrnesi. 



Fig. 1-5. Dorsal, ventral, front, cardinal and profile view of a speci- 

 men. Page 109 



Fig. 31-34, 36-39. A series of specimens, showing variety in form and 

 ornamentation. 



Spirifera gregaria. 



Fig. 6-10. Dorsal, ventral, front, cardinal and profile view of a speci- 

 men. Page 119 



Spirifera varicosa. 



Fig. 11-20, 23-25. A series of specimens showing variety in size, form 



and ornamentation. Page 134 



Spirifera hobbsi. 



Fig. 21, 22. Dorsal and ventral view of a specimen. Page 121 



Fig. 26-30. Dorsal, ventral, front, cardinal and lateral view of speci- 

 men. 



Fig. 35, 40. Dorsal and ventral view of a specimen, showing extreme 

 extension of hinge-line. 



