Plate 50. 



1, 2. Aspidodiadema nicobaricum D6d. 



1. Valve of stout tridentate pedicellaria. X 70. 



2. Sphseridium. x 70. 



3-5. Aspidodiadema tonsum A. Ag. 



3. Valve of stout tridentate pedicellaria, " form b." X 70. 



4. Valve of pedicellaria midway between tridentate and ophicephalous, " form c." X 70. 



5. Valve of broad triphyllous pedicellaria. X 70. 



6-10 Dermatodiadema globulosum A. Ag. 



6. Valve of stout tridentate pedicellaria. X 70. 



7. Valve of slender tridentate pedicellaria. X 70. 



8. Valve of triphyllous pedicellaria. X 70. 



9. Valve of ophicephalous pedicellaria. X 70. 



10. Sphsridium. X 70. 



11-lu. Dermatodiadema horridum A. Ag. 



11. Valve of stout tridentate pedicellaria. x 70. 



12. Valve of slender tridentate pedicellaria. X 70. 



13. Valve of triphyllous pedicellaria. X 70. 



14. Valve of ophicephalous pedicellaria. X 70. 



15. Upper end of stalk of pedicellaria. X 70. 



16-19. Cheetodiadema pallidum A. Ag. and CL 



16. Valve of tridentate pedicellaria (broken at tip). X 70. 



17. Side view of base of same, x 70. 



18. Valve of triphyllous pedicellaria. X 70. 



19. Calcareous particles from gills, x 70. 



20, 21. Leptodiadema purpureum A. Ag. and CI. 



20. Sphaeridia. X 70. 



21. Calcareous particles from pedicels. X 70. 



