PLATE IV. 



Trigonocidaris albida,/ 1-7. 



1. Specimen measuring 12.7""'- in iliam. from above. 



2. Same measuring li.?""- in diam. from aclinal side. 



3. Part of test of same specimen, more highly magnified. 



4. Spine of same specimen. 



5. One of the pedicellaria; of test. 



6. Younger specimen, measuring 4.75°'°- in diam. from above. 



7. Portion of test of same specimen. 



Podocidaris sculpta,/. S-15. 



8. Specimen measuring II""- in diam. from above. 



9. Anotlier specimen of about same size from actinal side. 



10. The same in profile. 



1 1 . Profile of a very large specimen, nat. size. 



12. Portion of test of same magnified. 



13. Portion of median interambulacral area of same, showing the tubercles, scrobicular 



circles of pedicellariae. 



14. Abactinal system of same. 



15. Section of a principal spine near edge of test, greatly magnified. 

 IG. One of the pedicellarioe. 



