GENERAL CLASSIFICATION 



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Conchs. 



Pholadarians {Boring-mussels). 

 Pholas. AspergiUum. 



Teredo. — 



Fistulana. 



Ascidians. 

 Ascidia. 

 Salpa. 

 Mammaria. 



Order 2. — Cephalic Molluscs. 



A distinct head and eyes, and two or four tentacles in the majority, jaws or a 

 proboscis at the mouth ; reproduction by copulation. 



The shell of those, which have one, never consists of two valves articulated at a 

 hinge. 



(1) Pteropods. 



Two opposite, swimming fins. 



Hyalea. 



Clio. 



Pneumoderma. 



(2) Gastropods. 

 (A) Straight body, united to the foot throughout the whole or nearly the 



