ARRANGEMEXT OP CUVIER. 15 



for a class of men who, in consequence, become experi- 

 enced seamen ; and the sale of them is an important 

 part of the business of many. At the opening of the 

 oyster season, in August, the line of dealers extends, as 

 do the vessels, a considerable distance. 



The term mollusca, it should be remarked, was first 

 employed by Cuvier ; but as it is applicable to other 

 groups of beings, the structure of which is soft and 

 which have no true skeleton, later naturalists have ex- 

 changed it for terms designating the peculiar characters 

 of the nervous system, which are so remarkable in this 

 great section, and on which the bond of union be- 

 tween its different classes alone depends. 



Cuvier divides the mollusca into the following' 

 classes : — 



CLASS. EXAMPLES. 



1. Cephalopoda, Cuttlefish, nautilus, belemnite, etc. 



2. Pteropoda, Clio, hralea, etc. 



3. Gasteropoda, Slugs, aquatic and terrestrial snails. 



4. AcEPHALA, Bivalve moUusks, as oysters, mussels. 



5. Brachiopoda, Terebratula, orbicula ; fixed bivalve moUusks, 



with peculiar characters, separating them from the acephala. 



6. CiRRHOPODA^ Barnacles, etc. 



It must be here observed, that Cuvier places two 

 families, which he terms, " Acephala, destitute of shells," 



