PLATE 31. 
Page 
Figs. 1-4 Spirifera varicosa . .. '.. 205 
1, 3,4. 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 segmenta. 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. Yentral, 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 Williamsville, New York. 
26 - 30. Dorsal, ventral, cardinal, front and profile views of a large imperfect specimen from N. 
York, which is much more extended laterally than the usual form. 
