TEREDO — MUSSEL. 



33 



very curious one. It is called the Ship-worm 

 because it has so powerful an appetite for sub- 

 merged wood, and especially for ship-timber. I 

 have now by me a large piece of oak, the remains 

 of some wreck, which I found entangled among 

 the rocks at low water. It is so completely 

 devoured by the Teredo, that it is almost im- 

 possible to find any portion of the wood that is 

 thicker than the sheet of paper upon which 

 this account is printed. Timber, however, can be 

 protected from the Teredo by a closely-studded 

 surface of broad-headed iron nails. These nails 

 soon rust through the action of the salt water, 

 and the whole of the timber is rapidly covered 

 with a thick coating of iron rust, a substance 

 to which the Teredo seems to have a strong 

 objection. 



The Teredo navalis is not a very large animal, 

 but it has a huge overgrown relation, the Giant 

 Teredo, whose diameter at the thickest part is 

 three inches, and its length nearly six feet. 



On plate b, fig. 8, may be seen a shell, which 

 will probably be recognised at once as the 

 Common Mussel {Mytilus edulis). The specimen 

 figured is a young one, and is shown as it 

 appears when adhering to the rock by means 

 of the natural cable — or byssus, as it is scienti- 



