PLATE XI. 



Mellita sexforis, f-l- 12. 



1. Young M. sexforis of a Laganum shape, no posterior interambulacral lunule seen from above, 2.4"""- 



in Jiam. 



2. Same from actinal side, deeply concave, showing commencement of hmule. 



3. Young, showing first trace of posterior interambulacral lunule, from above, 4.0°'"- in diam. 



4. Same from actinal side. 



5. Rotulae of same magnified. 



6. Posterior interambulacral lunule of specimen measuring 5.3"". in diam., magnified. 



7. Young specimen, measuring 7 S""- in diam., from above. 



8. Same from actinal side, no trace as yet of pits forming ambulacral lunules. 



9. Young specimen, mciisuring lO.l"""- in diam., from above, showing trace of the ambulacral lunules all 



unequally developed. 



10. The same from below, showing the deep pits, unequal in size, forming the rudimentary lunules. 



11. Young specimen, measuring 12.7°"»- in diam., with all the ambulacral lunules completely pierced 



through and well formed. 



12. Young specimen, measuring 38""' in diam., having all the the principal features of the adult. 



Mellita testudiuata,/ 13-22. 



13. Young, with scarcely a trace of notches and a well-formed posterior lunule; from above, nat. size. 



14. Posterior part of test of same from above, magnified. 



15. Somewhat older specimen than fig. 13. 



16. Magnified portion of test of same fi-om above. 



1 7. Magnified portion of test of same from below. 



18. Young specimen, older than fig. 15, with a trace of notches, commencement of ambulacral lunules. 



19. Young specimen, considerably older, with deep notches, nat size. 



20. Kotulae, with part of poriferous zone, of fig. 18, magnified. 



21. Part of ambulacral rosette of specimen measuring 60""- in diam. 



22. Diagram of arrangement of pores of Mellita testudinata. 



23. Diagram of arrangement of pores of Echinanthus rosaceus. 



Mellita longifissa,/ ^4-^. 



24. Young, nat. size, fi-om above; ambulacral notches commencing to close. 



25. Part of test of same, magnified. 



26. Young, nat. size, with ambulacral notches changed to lunules. 



27. Part of test of same, magnified. 



