PLATE 21. 



Page 



Fig. 1, 2 & 3. Strophodonta cavtjmbona. 187 



1 o, c. Ventral and dorsal valves of young specimens. 

 1 6, d. The striae in profile, and the surface enlarged. 

 1 c. A partial cast of the ventral valve. 

 ] /. The dorsal valve partially exfoliated, and showing the crenulations along the liinge-line : 



the striae are rounded and frequently bifurcating. 

 1 g. The punctate surface shown where the shell is exfoliated. 



1 h. Profile of the rounded strias of 1 /. 



2 a. The dorsal valve of a well-preserved specimen. 



2 c. Profile of strise, showing the elevations and flat surfaces between them. 

 8. A ventral valve, probably of this species. 



Fig. 4. Strophodonta puNCTULiFERA. 188 



4 a. A cast of this species. 



4 6. Enlargement of the striae, showing the punctate surface. 



Fig. 5, 6 & 7. Strophodonta leavenworthana. 189 



5 a. The dorsal valve, showing obscurely the concentric wrinkles and the punctate surface 



where the shell is exfoliated. 



6 a. Interior of the ventral valve. 

 6 b. Profile of the preceding. 



6 c, Enlargement of the crenulations of the hinge-line of 6 a. 



7 a. Interior of a ventral valve. 

 7 b. Profile of the same. 



Fig. 8 & 9. Strophodonta radiata. 193 



8 o. A figure of the original specimen, with the shell in part exfoliated. 



8 b. Enlargement of the radiating and concentric strise. 



9 o. A smaller individual from the same locality. 



9 b. Enlargement of surface when the shell is partially exfoliated. 



