PLATE I?. 



Cidaris metularia, /. 1. 



1. Seen from the abactinal pole. 



Goniocidaris canaliculata, /. 2. 



2. Seen in profile. 



Goniocidaris geranioides, /. S, i. 



3. Seen from the abactinul pole. 



4. Seen in profile. 



Arbacia pustulosa, /. 5. 



5. Seen from the above pole. 



Arbacia nigra, /. 6", 7. 



6. Seen from the actinal side. 



7. Seen from the abactinal pole. 



{All Fir/s. natural size.) 



