26 BULLETIN "4, UNITED STATES NATIONAL MUSEUM. 



EXPLANATION OF PLATES. 



Plate I. 

 Catorirfam micans (Morten'sen). Actinal side. X i- 



Plate 2. 

 Trelocidaris barllcUi (A. Agassiz). Abactinal side. X i- (Same specimen a.^ Plate 3.) 



Plate 3. 

 Tretocidaris bartktti (A. Agassiz). Actinal side. X h (Same specimen as Plate 2.) 



Plate 4. 

 Stylocidaris lineata, new specie.s. Actinal side. Natural size. (Same specimen as Plates 5 and 6.) 



Plate 5. 

 Stylocidaris lineata, new species. Abactinal side. Natural size. (Same specimen as Plates 4 and 6.) 



Plate 6. 

 Stylocidaris lineata, new species. Side view. Natural size. (Same specimen as Plates 4 and 5.) 



Pl.\te 7. 



(All figures natural .size.) 



Figs. 1-2. Cidaris abyssicola (A. Agassiz). 1. Abactinal side. 2. Side view; same specimen. 



3-5. Stylocidaris lineata, new species. 3. Side view. 4. Actinal side. 5. Abactinal side; 



same specimen. 

 6. Tretocidaris burtlctti (A. AgMsiz). Young specimen. Abactinal side. 



Pl.^.te 8. 



(Both figures natural size.) 



Fig. L Cidaris abyssicola {A. Agassiz). Actinal side. 

 2. Cidaris abyssicola (A. Agassiz). Side view. 



Plate 9. 



Natural size. 



Figs. 1-2. Cidaris abyssicola, var. terelispina Mortensen. 1. Actinal side. 2. Abactinal side; same 

 specimen. 



Plate 10. 



(Both figures natural size.) 



Fig. 1. Cidaris abyssicola, var. terelispina Mortensen. Side view. (Same specimen as Plate 9.) 

 2. Cidaris abyssicola, var. terelispina. Actinal side; same specimen. 



Plate 11. 



Figs. 1-2. ^Ira-osoma 6cZK Mortensen. X J. 1- Abactinal side. 2. Actinal side; same specimen. 



Figure 1 is made up from two different photographs; the left side was made to show the undenuded 

 part of the test, the right to show the denuded part as clearly as possible, the color of these two parts 

 contrasting so much as to make it impo.ssible to represent both parts clearly in the same photograph. 



Plate 12. 



Fig. 1. Arxosoma belli }ilortensen. Actinal side. Natural size. 



2. Arxosoma fenestratum (Wyville Thomson). Actinal side. X }. 



