MOLLUSCA. 181 



shell cameo of the same description, unless of extra 

 ordinary merit, would rarely fetch fifty francs (2). 



Cameos are executed on shells as on stones; 

 the subject is worked in relievo on the white 

 portion or outer crust of the shell, while the inner 

 surface, of a pink or brown tint, is left for the 

 ground. Cameo artists who work upon shells are 

 to be met with in London and Paris. The only 

 shells that I have seen employed are the Conch 

 shell (Strombus gigas) and the Helmet shell (Cassis) 

 among the Gasteropoda, and the shells of the genus 

 Chama. The latter mollusc inhabits the inter- 

 tropical seas ; the species lives fixed to the rocks ; 

 and its foot (or under part of the body by which the 

 animal moves) is remarkable from being bent, and 

 resembling in form the foot of a man. The species 

 known to the French as the Came feuilletee is one 

 of the most curious, and may be taken as a type of 

 the group. The superior valve of the shell is com- 

 posed of superposed plates or layers of calcareous 

 matter of different colours. The cameos made from 

 it resemble closely those cut upon agate or onyx. 



I have seen very beautiful cameos cut in Paris 

 upon the ordinary Conch shell (Strombus gigas), 

 and sell at eighty francs (3 6s.). Probably other 

 shells might be found to answer the same purpose ; 

 it is sufficient that they present two or more layers 

 of different colours, which is not unfrequently the 



