PLATE 35. 



Page 



Figs. 1-9. ' Spiripera tullia 218 



1-3. Views of dorsal valves, one of them showing rugose markings on the plications. 



4. A ventral valve of the ordinary form. 



6. 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 8CULPTILIS 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. 



18, 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 



16. 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. 

 28. Interior of ventral valve, showing the extension of the dental lamcUce into the body of the 

 abeU. 



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. 



