236 POPULAR CONCHOLOGY. 



with eyes in the middle; foot large. — 25 spe- 

 cies recent, and 1 fossil. 



These animals sometimes grow to a very 

 large size, requiring of course a corresponding 

 magnitude of shell. They are chiefly brought 

 from the Indian seas, but a few species are 

 found in the Mediterranean; they live at 

 some distance from the shore on the sand, into 

 which they occasionally burrow, and entirely 

 hide themselves. In some species the columel- 

 lar lip projects above the spire, giving a flat 

 appearance to the lower part of the shell. 



The shells of the Cassis rufa and other spe- 

 cies are exquisitely sculptured by Italian artists 

 in imitation of antique cameos, the different 

 strata of colouring matter resembling those of 

 the onyx and other precious stones. Of these 

 a great variety of ornaments are made, and of 

 late years a considerable trade has been carried 

 on in them on the Continent. The substance 

 of shells seems to be formed of three plates, 

 the central generally being the thickest, and 

 the outer one the thinnest. The Italian cameo 

 cutters appear to be aware of this circum- 

 stance, and avail themselves of it in cutting the 



