124 



Plate II. 

 Derbya multistriata (Meek). 



1. Brachial valve of sijeeimen w^ith high area extending nearly back- 

 ward, due partly to compression. 



2. Same view of another specimen with low beak and normal brachial 

 valve. 



3. Pedicle valve of another specimen showing surface marks and thir- 

 teen young specimens adhering to it. They are of the same species. 



3a. Profile of number 3. Pedicle valve uppermost. 



4. A profile of another and smaller specimen with a high and dis- 

 torted hinge area. I'edicle valve uppermost. 



All figures natural size. 



