CUTTLES AND SQUIDS — GASTROPODS 



3°3 



Belonging to the same family (Sepiolidw) is another British genus, Rossia, which 

 differs in having the dorsal surface of the investing " mantle " strengthened by a 

 ridge instead of being united with the head by a band. 



In the true cuttles of the family Sepiidcv the pen is replaced by the so-called 

 " cuttle-bone," which has a thin horny margin, is oval in shape, thick in front 

 with the hind-end hollow and furnished with a spine. The common cuttle (Sepia 

 officinalis) of European seas is notable on account of the unusual beauty of its 



THE OCTOPUS. 



Gastropods. 



coloration, the back being generally brownish spotted with white, while the under- 

 pays are paler and the sides violet, with the arms or tentacles greenish. 



In the northern seas, as elsewhere, the gastropods or univalves 

 are more numerously represented than any other class of the Mollusca, 

 but a mere list of their genera would occupy so many pages that we must restrict 

 our remarks to a few of the more familiar or those of interest from our special 

 point of view. The common whelk (Buccinum undatum), for instance, ranges 

 from the coast of Norway to the east coast of the United States north of Cape Cod 

 Bay. The family (Buccinidai) is widely dispersed in the northern and Antarctic 

 seas, and one representative, Euthria cornea, affords a striking instance of discon- 



