124 



Plate II. 

 Derbya muUistriata (Meek). 



1. Brachial valve of specimen with high area extending nearlj- 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 j-oung 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. Pedicle valve uppermost. 



All figures natural size. 



