VI. Description of the Plates. 



PLATE I. 



Figure 1. Cidaris lacrymula, Duncan and Sladen (page 8). The test seen in profilej natural 

 size. 



2. The same, magnified. 



3. A portion of the ambulacral area, magnified. 



4. Profile outline of the same. 



5. Interambulacral plate, magnified. 



6. A primary tubercle seen in profile, magnified. 



7. A portion of the scrobicular ring, showing the shield-shaped boss of the tubercle and the 



tear-shaped mamelon, magnified. 



8. Plesiolampas elongata, Duncan and Sladen (page 10). Abactinal aspect of the test, 



natural size. 



9. Actinal aspect of the test, natural size. 



10. Outline of the longitudinal profile of the test. 



11. Outline of the transverse profile of the test. 



12. Apical system, magnified. 



13. A portion of the ambidacral and interambulacral areas, magnified. 



14. The part of an ambulacrum near the peristome, magnified. 



15. Tubercles on the actinal surface, magnified. 



16. Tubercles near the ambitus, magnified. 



