PLATE XXXV. 



1. Cidaris tribuloides. Longitudinal section of base of large primary interambulacral spine. 



2. Cidaris Thouarsii. Transverse section of shaft of large primary interambulacral spine. 



3. Cidaris metularia. Transverse section of shaft of large primary interambulacral spine. 



4. Phyllacanthus baculosa. Longitudinal section of base of large primary interambulacral 



spine. 



5. Goniocidaris geranioides. Transverse section of shaft of large primary interambulacral 



spine. 



6. Transverse section of shaft of spine of Acrosalenia from the Jurassic formation. 



7. Arbacia spatuligera. Transverse section near base of large primary interambulacral spine. 



8. Arbacia punctulata. Longitudinal section of large primary interamliulacral spine. 



9. Arbacia puuctulata. Transverse section near tip of shaft of large primary interambula- 



cral spine. 



Eohinothriz calamaris, /. 10-15. 



10. Longitudinal section of base of large primary interambulacral spine. 



11. Transverse section of Fig. 10 near base. 



12. Transverse section of Fig. 10 near middle of shaft. 

 1.3. Longitudinal section of small interambulacral spine. 



14. Longitudinal section of part of small ambulacral spine. 



15. Transverse section of ambulacral spine. 



16. Salenia varispina. Transverse section of large primary interambulacral spine. 



