DESCRIPTION OF PLATE LXIX— Continued. 591 



Page 

 Fig. 8. Prodiietua semiretictilatus 535 



a. Ventral valve, posterior view. 



b. Lateral aspect of same. 



c. Outline as seen from above. 



Madison limestone, Crowfoot Ridge, Gallatin Range, lower part of bed 27. 



d. Dorsal valve of same species. 



Madison limestone, head of Conant Creek, Teton Range. 



Fig. 9. Productus Iwvicosta 531 



a. Ventral valve of a specimen from Utah, restored ; after Hall and Whitfield. 



Waverly age, Dry Canyon, Utah. 

 6. A ventral valve from the Madison limestone, flafand immature in expression. 



Madison limestone, Crowfoot Ridge, Gallatin Range, top of bed 25. 

 c. Lateral outline of a ventral valve of the usual type. 



Madison limestone, Crowfoot Ridge, Gallatin Range, lower part of bed 27. 



