PLATE 31. 



Page 

 Figs. 1-4 Spirifera varicosa 205 



1,8,4. Dorsal, ventral and cardinal views of a specimen of the ordinary size and form of those 



from the Falls of the Ohio. 

 2. Dorsal view of another individual, showing a more strongly rugose surface. From the same 



locality as the preceding. 



Fig. 23. Spirifera varicosa var 206 



23. A ventral valve with the hinge line much extended, from Western New York. 



Figs. 5-8. Spirifera seomenta 207 



5-8. Dorsal, ventral, cardinal and profile views of the original specimen of this species, from 

 the Falls of the Ohio. 



Figs. 9, 10. Spirifera arctiseqmenta 208 



9, 10. Dorsal and cardinal views of the original specimen. 



Figs. 11-13. Spirifera euruteines var. fornacula 211 



11 - 13. Dorsal, ventral and cardinal views of a specimen from Bake-oven, Illinois. 



Figs. 14 - 19. Spirifera euruteines 209 



14 - 17. Ventral, cardinal, profile and dorsal views of a specimen of ordinary size and form. 



18. The interior of a ventral valve containing the spires, which are covered with chalcedony. 



19. A cardinal view of a young individual. 



Figs. 20 - 22, 24 - 30. Spirifera manni 211 



20-22. Dorsal, cardinal, and front views of a characteristic specimen, from near Sandusky, Ohio. 

 24, 25. Dorsal and cardinal views of an imperfect specimen, from Williiimaville, New York. 

 26 - 80. Dor.sal, ventral, cardinal, front and profile views of a large imperfect specimen fVom N. 

 York, which is much more extended laterally than the usual form. 



