PLATE X. 



Figure 1. Progonechinus Eocenicus, Duncan and Sladen (page 48), natural size. 



2. An ambulacrum and part of an interradium^ magnified. 



3. A portion of the test near the actinostome, magnified. 



4. A side view of the test, natural size. 



5. DiCTYOPLEURUs d'Archiaci, Duncan and Sladen (page. 41), natural size. 



6. An ambulacrum and part of an interradium, magnified. 



7. A weathered specimen^ natural size. 



8. The same, part of an ambulacrum and interradium, magnified. 



9. A spine of a species of Cidaris (page 50) , natural size. 



10. A portion, magnified. 



11. A spine of a sj)ecies of Cidaris (page 50), natural size. 



12. A portion, magnified. 



13. A small spine of a Cidaris (page 50), natural size. 



14. The ring around the cavity for the tubercle, showing incomplete crenulation, magnified. 



