EXPLANATION OF THE PLATES. 



PLATE I. 



1, -2. Astropyga pulvinata, two thirds natural size. 

 3, 4. Arbacia Dufresnii, natural size. 

 5-7. Coelopleurus floridanus, — 5, natural size ; 6, 7, four times natural size. 



PLATE II. 



1, 2. Asthenosoma hystrix, two tliirils natural size. 

 3-. r >. Nacospatangus gracilis, natural mz<', 17""-. 

 6. Echinus margaritaceus, natural size. 



PLATE III. 



1-3. Monophora Darwinii, natural size. 

 1. Echinus margaritaceus. natural size. 

 "i. Echinus magellanicus, natural size. 



1' I. ATE IV. 



1-3. Paleopneustea cristatus, two third) natural die. 

 ■1 - 8. Hemiaster Philippii, natural size. 



