INTRODUCTION. 3 



of every system^ and the greater their number, the more 

 necessary it becomes to subdivide them ; if, for instance, all 

 the species now known were to have been included in the 50 

 genera of Linn^us, a single genus would have contained 

 many hundreds of incongruous species, in which case it would 

 be much more difficult to remember them, than if they were 

 to be divided into a far greater number of genera. Every 

 well marked division, tends to simplify the subject, and to 

 facilitate the researches of the student. 



NATUEE OF THE SCIENCE. 



Conchology is the study of shells, viewed and described as 

 to what they are either in themselves, or in relation to the 

 soft, inarticulate animals which produce them, and of which 

 they form a part. These animals are called Mollusca, and 

 perhaps the best general description of them will be found in 

 De Blainville's "Manuel de Malacologie et de Conchyhologie." 

 The following is a translation, "Animal in pairs, the body and 

 its appendages soft, inarticulate (not jointed), enveloped in a 

 muscular skin, commonly called the mantle, which is ex- 

 tremely variable in form, and has developed either within or 

 upon it a calcareous portion, consisting of one or several 

 pieces, commonly called a shell.^' 



The term Mollusca was formerly restricted to those soft 

 animals which were destitute of shells, although possessing 

 in other particulars, the characters described above, and it was 

 used in order to distinguish them from the Te stage a, which 

 were covered or internally supported by calcareous parts. In 

 the system of Linnseus, the soft portions are first arranged 

 under the general designation of " Vermes Mollusca," and 

 described without regard to the presence, absence, or cha- 

 racter of the shells; and then the shells are separately 



B 2 



