PLATE 11. 



Pag« 



Figs. 1-8. Strophodonta alveata 81 



1. The interior of a dorsal valve as obtained ft-om a cast in the Schoharie grit. 



2. The cast of a ventral valve. 



8. A smaller ventral valve of the same species. 



Figs. 4-10. Strophodonta callosa , 82 



4. Interior of a dorsal valve, iVom an impression in the natural mould, showing muscular impres- 

 sions and cardinal process ; enlarged to two diameters. 

 6, 7. Casts of ventral valves, natural size. 



8. Interior of the dorsal valve, from an impression in the natural mould, showing muscular 



impressions, cardinal process, and the crenulatt'd hinge line ; enlarged to two diamett^rs. 



9, 10. Cardinal and ventral views of a cast of a ventral valve, showing the muscular impres- 



sions very distinctly; enlarged to two diameters. 



Figs. 5, 11. Strophodonta parva 85 



6. Impression of a dorsal valve of this species. 

 11. Cast of a ventral valve, enlarged to two diameters, showing muscular impressions and the 

 crenulated hinge. 



Figs. 12, 13, 18 - 21. Strophodonta crebristriata 86 



12. Exterior of a small ventral valve. 



13. Exterior of a smaller ventral valve, enlarged to two diameters. 

 18, 19. Exterior and profile of a larger ventral valve. 



20. Enlargement of the surface striiE. 



21. Exterior of a very large ventral valve. 



23. Interior of a dorsal valve, from an impression in the natural mould. Doubtfully referred 



to this species. 



Figs. 14 - 17. Strophodonta demissa 81 



14. View of a ventral valve taken from an impression left in the Schoharie grit by the decay of 



the shell. 

 16. Internal cast of a ventral valve in the grit. 



16. Interior of a dorsal valve, showing the muscular impressions and cardinal process. 



17. Cast of the interior of a ventral valve, showing the muscular impressions in a very perfect 



manner. From the soft shales of the Hamilton group. 



Fig. 22. Strophodonta perplana 92 



22. An impression of a ventral valve of this species. 



Figs. 24-31. Strophodonta iNKQCiRADiATA 87 



24, 25. Profile, and vertical view of a ventral valve with distant coarse stria). 



26. View of a cast of a ventral valve showing a narrow muscular impression. 



27, 28. Front and cardinal views of a cast of a ventral valve, showing muscular and vascular 



impressions in a very perfect manner. 

 29. Cast of a large ventral valve. 

 80, 31. Impressions of the exteriors of dorsal valves, showing sharp distant strise. 



