PLATE XXI. 



Figure 1. Leiocidaris canaliculata, Duncan and Sladen (page 109). The test seen in profile, 

 natural size. 



2. Actinal view of a part of the test, natural size. 



3. Plates of the interambulacral area, magnified. 



4. Ambulacral plates, a little above the ambitus, magnified. 



5. Ambulacral plates from a larger specimen, at the ambitus, magnified. 



6. Ideal section of an ambulacral area. 



7. A portion of a spine, magnified. 



8. A young specimen, seen in profile, magnified. 



9. Ambulacral plates from the same, magnified. 



10. PoRociDAKis ANOMALA, Duucau ^nd Sladen (page 113). The test seen in profile, 



natural size. 



11. Actinal view of a part of the test, natural size. 



12. An interambulacral plate with the adjacent portion of the ambulacral area, magnified. 



(The scrobicule ought to be more distinctly oval transversely than represented in this 

 figure, or in Figure 10.) 



13. Ambulacral plates, magnified. 



14. Outline of a fragment of a spine, slightly magnified. 



