INTKODUCTION. 



CHAPTER I. 



CLASSIFICATION. 



DEFINITION OP THE TEEM ''CONCHOLOGY." CONFORMITY OF 



SHELLS WITH THEIR INHABITANTS. CEPHALIC MOLLUSKS OR 



UNIVALVES. ACEPHALA OR BIVALVES. TUNICATA. SPE- 

 CIES. VARIETIES. MONSTROSITIES. REVERSED SHELLS. 



SYNONYMY. NOMENCLATURE. 



Definition of the term " Conchology .'^ — Conchology ^, 

 as a branch of Natiu'al History, treats of the Molhisca 

 or that great division of invertebrate animals which have 

 soft bodies and an organization superior to that of 

 insects and only inferior to that of fishes. It properly 

 comprises the study, not only of the shell or outer cover- 

 ing of the moUusk, but also of the whole animal, — al- 

 though it has sometimes been used in a more limited 

 sense, in contradistinction to the term "malacology/^ 

 which has exclusive reference to the soft parts of the 

 animal. Linne included the Mollusca in his great class 

 Vermes — some of them as Vermes Mollusca and others 

 as Vermes Testacea ; but as the first of these divisions 

 comprised a very heterogeneous assemblage of inver- 

 tebrate animals, and as the testaceous Annelids were 

 united with the latter, the classification proposed by him 



* Compounded of two Greek words, Koyxri, a shellfish, and Xdyo?, a 

 treatise. 



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