28, 29. Strongylocentrotus fragilis Jackson. 



28. Side view of valve of globiferous pedicellaria. X 70. 



29. Base of same. X 70. 



30-33. Strongylocentrotus polyacanthus A. Ag. and CI. 



30. Tridcntate pedicellaria. X 70. 



31. Side view of blade of valve of globiferous pedicellaria. X 70. 



32. Base of a similar valve. X 70. 



33. Valve of ophicephalous pedicellaria. X 70. 



