Figs.. 1 -9. 
PLATE 35. 
Spirifera tullia . 
Page 
218 
1-3. Views of dorsal valves, one of them showing rugose markings on the plications. 
4. A ventral valve of the ordinary form. 
5. Cardinal view of a ventral valve, showing area and foramen. 
6. View of a ventral valve, having the cardinal extremities unusually extended. 
7. 8, 9. Casts of ventral valves of this species, showing great variations in the rostral portions 
of the shell. 
Figs. 10 -14. Spirifera sculptilis. 221 
10. Dorsal valve of this species, from which the shell is partly exfoliated". 
11. View of the ventral valve, showing the strong concentric ridges. 
12. Cardinal view of the ventral valve, showing area and foramen. 
13,14. Dorsal and ventral views of a specimen, which is with doubt, referred to this species—• 
the concentric ridges being more closely arranged and finer than in the preceding figures. 
Figs. 15-23. Spirifera ziczac. .. 222 
15. Dorsal view of a small individual. 
16, 17. Dorsal and ventral views of an individual of ordinary size. 
18 - 22. Dorsal, ventral, profile, front and cardinal views of a large and well preserved individual. 
23. Interior of ventral valve, showing the extension of the dental lamellae into the body of the 
shell. 
Figs. 24, 25. Spirifera acuminata ..._. * . 234 
24. Dorsal valve of this species, showing the bifurcating plications and the angular mesial fold. 
25. Cast of a ventral valve, showing the strongly marked muscular impression and the filling 
of the rostral portions of the shell. 
