PLATE IV. 



Diadema setosum, f. 1. 



1. Seen in profile. 



Strongylocentrotus Drbbachiensis, /. 2, 3, G. 



2. Seen from abactinal pole. 



3. Same, seen in profile. 



6. Seen from actinal side ; nat. size. 



Toxopneustes variegatus, f. i, 5. 



4. Seen from abactinal pole. 



5. Seen from actinal side. 



(^All Jigs. I natural dze, except Jirj. G.) 



