TEREDO. 113 



however to be no more reason for classing these 

 shells with the multivalves, than Turbines and others^ 

 which possess an operculunij with the bivalves. The 

 only difference between the lid of the Teredo and 

 that of a Turbo is, that the one is constructed of 

 four pieces, the other of a single disk. These pieces 

 cannot constitute the shell, because the animal can- 

 not be said to inkahit them, as it does the testa- 

 ceous tube. Neither is there any analogy between 

 them and the accessory valves of Pholas. 



At first sight the Teredo may easily be mistaken 

 for a Serpula, and in many cabinet specimens the 

 valves are lost. There are, however, but three spe- 

 cies of the former genus at present known, and their 

 external characters are soon to be distinguished. 

 The first, T. iiavalis, which is the most common, 

 is much more thin and brittle than Serpulae in ge- 

 neral, especially towards the smaller end. 



The name Teredo, or rsqrilojv, is derived from 

 Tsgeco, to lore, and is sufficiently descriptive of the 

 mode in which all the species effect their settle - 

 ment. 



