PLATE XXXVI. 



1. Ecbinometra lucunter. Transverse section of shaft of primary intpramlnilacral spine. 



2. Stomopueustes variolaris. Transverse section of shaft of primary interamV.ulacral spine. 



3. Longituilinal st-ctinn f)f primary interamhulacral spine of Stomopneustes variolaris. 



4. Strongylocentrotus tuberculatus. Transverse section of primary interamliulacral spine. 



5. Echiuometra oblonga. Lonj^itudinal section of primary- interamhulairal spine. 



6. Colobocentrotus atratus. Longitudinal section of primary interanilnihicral spine from 



aniliitus. 



7. Longitudinal section of short ahactinal primary interambulacral spine of Colobocentrotus 



atratus. 



8. Heterocentrotus mammillatus. Transverse section of shaft of large primary interambu- 



lacral spine. 



9. Strongylocentrotus purpuratus. Transverse section of primary- interamhulacral spine. 



10. Phymosoma crenulare. Longitudinal section of large primary interamhulacr.al spine. 



11. Transverse section of primarj- interamhulacral spine of Phymosoma crenulare. 



12. Hemipedina cubensis. Transverse section of large primary interambulacral spine. 



13. Trigonocidaris albida. Transverse section of large primary interambulacral spine. 



14. Temnopleurus Hardwickii Longitudinal section of primary interambulacral spine. 



