PLATE XIX. 



FIQ. 



1. — 9. — Probably varieties of the same species of Polycystin in the 

 Barbados deposit. They frequently assume a triangular ap- 

 pearance, there are no wide external openings visible, — but 

 Dr. Wallich has detected small 0})enings, which he compares 

 to a "Cat's claw," at the roots of the spines. 



