PLATE 28. 



Page 

 Figs. 1- 11. Spirifera qreqaria 196 



1. Dorsal view of a young individual. 



2. A dorsal view of a specimen of tlie ordinary size and form. 



3-6. Ventral, dorsal, profile and front views, of a large and gibbous form. 



7, 8. Interiors of ventral valves. These specimens are from the Falls of the Ohio. 



9, 10. Dorsal and cardinal views of a cast of this species in chert, from Indiana. This speci- 

 men shows a distinct depression in the mesial fold wliich is not a usual feature. 



11. The interior of a ventral valve and part of a dorsal, showing the crura and the last turns 

 of the spire. From the Falls of the Ohio. 



Figs. 12 - 16. Spirifera Formosa 220 



12 - 16 Dorsal, cardinal, profile, front and ventral views of the typical specimen of the species. 



Figs. 17-23. Spirifera orieri 194 



17 - 20. Four views of a specimen of small or medium size. 



21. A dorsal view of a large specimen, showing several plications on the mesial fold. 



22 A ventral valve, where the hinge is much extended, and the plications are less defined in the 



mesial depression. 

 23. A front view of the specimen fig. 21. 



In the collections of the Canadian Geological Survey, there is a specimen of this species 

 of much larger size than those observed or figured among the New Tork collections. 



Figs. 24 - 33. Spirifera duodenaria 189 



24,26,29,80,31. Dorsal, ventral, front, cardinal and profile views of a well formed and char- 

 acteristic specimen of medium size. 

 25, 28, 32. Dorsal, ventral and profile views of a more gibbous form. 

 27. Ventral view of a large individual. 

 33. The interior of a small ventral valve. 



