EXPLANATION OF PLATE VII. 

 (Figures 3-13 after Clark.) 



CIDARIS SPLENDENS (Morton), p. 279 



1-2. Two views of a nearly complete test. (Illustrations con- 

 tributed by Dr. W. B. Clark.) 



3. Portion of a test. 



4. Interambulacral plate (x2). 



5. Ambulacral area, highly magnified. 



6. Tubercle, enlarged. 



7. Spine. 



g. Base of spine much enlarged. 



9. Articular surface of spine, much enlarged. 



Vincentown limesand; Vincentown. 



CIDARIS WALCOTTI Clark, p. 281 



10. Portion of test, natural size. 



11. Interambulacral plates, enlarged. 



12. Ambulacral area, highly magnified. 



13. Tubercle enlarged. 



Vincentou.ni limesand; Vincentown. 



894 



