SHELLS. 233 



When at rest, the Cyprsea remains buried under 

 the sand at the bottom of the sea at a short distance 

 from the shore ; it occasionally traverses the rocks 

 and coast, and may be found under stones and corals. 



3. Genus Colombella. — These are small, short, and in 

 general prettily coloured shells. Colombella mercatoria 

 is the only species of the genus known at Bermuda, 



4. Genus Buccinum (Whelks) comprises aU the 

 shells furnished with an emargination, or short canal, 

 bent to the left, and whose columella is not plaited. 



The following species are generally found on our 

 shores — viz. Buccinum undatum, Buccinum lunatum, 

 and Buccinum reticulatum. 



5. Genus Purpura. — The species are two : Pur- 

 pura patulata. — It was from the animal of this 

 species that the Roman purple dye was obtained. 

 The shell is ovate, transversely sulcate, tubercular, 

 reddish black ; spire, shortish ; aperture, patulous ; 

 columella, reddish yellow ; outer lip, white within. 

 The other species — Purpura lapillus — affords also a 

 purple dye. The colouring matter occurs in a vesi- 

 cular reservoir near the stomach. It is no longer 

 used, however, the discovery of cochineal having 

 furnished an abundant supply of equally beautiful 

 and more easily procured colour. 



6. Genus Cassis. — The shells of the Cassis rufa 



