PLATE V. 



Arbacia punctulata, f. 1- IS. 



1. Seen in profile, somewhat reduced, with the tentacles fully expanded. 



2. Same, seen from above (part of test). 



3. (Somewhat magnified) profile view of the abactinal part of the test, showing the pointed 



tentacles. 



4. A single disk bearing tentacle, one of the ten near the actinostome. 



5. Cluster of gills. 



6, 7. Pointed tentacles, from the flat side. 



8. Pointed tentacle, from the narrow side. 



9. Young, measuring 2.11""- in diameter, from above. 



10. Abactinal system and part of test of specimen of nearly the same size as in fig. 9. 



11. The same portion of test of a specimen very slightly older. 



12. Spine of fig. 9, magnified. 



13. Spine of specimen of the size of fig. 14. 



14. Young specimen, measuring 4.2"°' in diam. from above. 



15. Actinal view of same. 



16. Young, measuring 7.5"°" in diam., first appearance of pedicellarite. 



17. Spine of specimen of size of fig. 16. 



18. Young, measuring lO.S""- in diam., having all features of adult. 



Arbacia pustulosa, /. 19-21. 



19. Young, measuring 4.0""- in diam. from above. 



20. Young, measuring 3.1"". in diam. from above. 



21. Young, measming 7.2""- in diam. from above. 



