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 

 Ohama. 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 



