INTRODUCTION. XV 



ceive, when we consider how readily the lobster 

 quits its crustaceous covering, and the crab gets rid 

 of its claw. 



When the cowry has completely abandoned its 

 shell, it is quite naked, and exposed to the imme- 

 diate influence of the sea. From the irritation occa- 

 sioned by the salt water, or from some other cause 

 of which we are ignorant, the hinder parts of the 

 body again begin to furnish the testaceous matter, 

 which is afterwards condensed upon the surface. 

 This secretion is continued till, at length, the shell 

 appears of the consistence of paper, and the mouth, 

 which at this period is very wide, soon afterwards con- 

 tracts to its proper shape. The wings of the ani- 

 mal, folded upon its convex surface, thicken and 

 form the teeth, which are seen on the edge of the 

 mouth, and which are deposited with the enamel 

 that adorns the external part of the shell. In this 

 manner is produced the opaque and highly po- 

 lished surface, which is so eminently beautiful in the 

 full-grown cowry, and which, by the colour of its 

 spots, or stains, contributes greatly towards distin- 

 guishing the different species of the genus. 



Bivalve shells, such as Muscles, Oysters, &c, in- 

 crease by adding to their whole circumference, or 

 rather to all the edge, except the hinge ; and every 

 experiment that has been made upon the subject, 



