ORDER BIMUSCULOSA. 



89 



The Ship-AVorm, {Teredo navalis.) 

 Before the anatomy of this destructive creature had 

 been Ccirefully examined, there was as much difficulty 

 in guessing at the means it employed in penetrating 

 the solid timbers in which it is found, as there is with 

 regard to the operations of the Pholas ; but subsequent 

 observation shows that the hard parts, of which the 

 mouth is formed, are fully equal to the task. 



Teredo navalis. 



Perhaps v.-e may say, with propriety, that this is the 

 only species of the shell-bearing tribes that is decidedly 

 injurious to mankind. The animal of the Teredo is a 

 long worm- shaped creature, dwelling in a tube of a 

 shelly substance, which it forms for itself in its progress 

 through the wcod ; the small pointed shell-like pieces, to 

 the right in the engraving, form the jaws of the animal. 

 "With the assistance of these it cuts its way into the 

 timber, and, at the same time, lines the excavation it is 

 making with a shelly substance, which is gradually 

 formed into a tube, the animal occupying that part which 

 is most deeply sunken in the timber; in directing its 



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