THE PHYLUM MOLLUSCA 



fication of the entire organization in relation to a mode of feeding which is 

 unusual among the other classes. 



THE CLASS AMPHINEURA 



The amphineurans are well exemplified by the chitons, or "armadillo 

 snails." These mollusks are frequently encountered at the seashore, although 

 in numbers of species and in abundance they are insignificant when compared 

 with pelecypods or gastropods. The shell consists of eight dorsal plates, in 



Fig. 13.9. Shipworms and their activities. A, por- 

 tion of a wharf timber extensively damaged by the 

 burrowing activities of these bivalves. When the 

 burrows are fresh and occupied, they are lined by 

 a calcareous layer secreted by the animal. 5, a 

 shipworm, Bankia canbbea, removed from its bur- 

 row; note the elongate bodv, the extended siphons, 

 and the strongly reduced valves of the shell which 

 function as cutting plates in boring through wood. 

 {A, photograph by Bassett Maguire, Jr.; B, photo- 

 graph by Eugene S. Clark, Jr.) 



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