274 POPULAR BRITISH CONCHOLOGY. 



conversation. But in scientific works it is usually judged 

 more correct to use terms of strictly technical application. 



The purpose of this chapter is to enable the uninitiated 

 to understand some of the technicalities referred to. Thus, 

 it will be seen, a different plan is here pursued from that 

 which generally obtains. Tor, in most books of an ele- 

 mentary character, it is usual to hegin with the A, B, C, or 

 with such phrases as " Grammar is the art of," etc., or " The 

 science of Conchology teaches/^ etc. But in this work it 

 has been my endeavour to avoid all these technicalities in 

 the outset as much as possible, so as not to weary the reader 

 before he is sufficiently interested in the subject to wish for 

 their acquaintance. 



The details to which the reader is now to be introduced 

 however will apply particularly to the conchological part of 

 the science. We have been speaking of mollusca as animals, 

 each one as to its habits, its shape, its appendages, testaceous 

 or otherwise; we are now to consider the shell alone, and 

 to inquire, " How is the shell of any particular mollusc de- 

 scribed and distinguished from that of any other ? " 



THE SHELL OP A TRUE MOLLUSC 



Must be distinguished from three other kinds of tests pos- 



