EXPLANATION OF THE PLATES. 



PLATE I. 



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

 3, 4. Arbacia Dufresuii, natural size. 

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



PLATE II. 



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

 3-5. Nacospatangus gracilis, natural size, H""-. 

 6. Echinus margaritaceus, natural .size. 



PLATE III. 



1-3. Monophora Darwinii, natural size. 



4. Echinus margaritaceus, natural size. 



5. Echinus magellanicus, natural size. 



PLATE IV. 



1-3. Paleopneustes cristatus, two thirds natural size. 

 4-8. Hemiaster Philippii, natural size. 



