GEOWTH OF SHELLS. 157 



of a chamber which the animal has outgrown 

 and vacated, he does not again enter the ' halls 

 of the past,' but deliberately shuts out the past 

 and its injuries alike, by building a shelly wall 

 or partition entirely across that part of the 

 shell. 



" The different depositions or layers are 

 sometimes shown when the edges of a shell be- 

 come broken. They are also seen in the cameo 

 shells, in which the laminations are of different 

 colors. You will see what I mean by this," 

 she said, unfastening from her collar a brooch 

 of shell cameo. Holding it to the light she 

 displayed the delicate translucence of the 

 orange ground over which figures were carved 

 from the next layer in white relief. " This 

 shows the strata of the shell," she said, "and 

 also how the colors have been turned to account 

 in carving the Jewel. The shell from which this 

 was cut was known as Cassis cornuta ; its habi- 

 tat was the Indian Ocean. 



" All cameos are not colored like this. Some 

 are a pale salmon on an orange ground. Such 

 are cut from the Cassis rufa. Others, from C. 

 Madagascariensis and C. tuberosa, have white 

 figures on dark claret-colored ground. Some 

 are cut from the Strombus gigas, which is the 

 pinky queen's couch of the West Indies. These 



