14 INTRODUCTION TO CONCHOLOGY. 



remembrances of her sailor boy, and the costly cabinets of 

 the shell collector. 



The inner portion, or rather columella, with its spiral 

 compartments, however, remains undisturbed. The animal 

 inhabitant merely dissolves the outer portion of his shell 

 with an acetous juice, exuding from his mantle, wliich is 

 capable of being extended over the shell; and the same 

 power which enables him to furnish his last coating of 

 enamel can be exerted in the formation of superior cumbent 

 layers to replace what he has thought proper to remove. 

 Thus, also, the Murex readily displaces spines, or any similar 

 obstacles which impede an enlarged growth; while the 

 PJiolades, as already noticed, and other terebrating mollusks, 

 exercise a faculty which enables them to penetrate the 

 hardest limestone rocks. 



The structure of the Cowry shell is, moreover, peculiarly 

 tenacious of absorption ; it is composed of a larger quantity 

 of carbonate of lime tlian membranous substance, — a fact 

 which readily accounts for its surface becoming vitrified or 

 polished by continual contact with the acid secretions of the 

 mantle. And as respects the formation of a new shell, it is 

 worthy of remark, that the glutinous matter which resembles 

 shell-lac, and is so fragile as to crack with the slightest 



