TEREDO. 123 



have ; the hinge is in articulated or jointress, although some- 

 times furnished with tubercular processes : apophyses falci- 

 form, springing outwards from beneath the hinge, one in 

 each valve : scars seldom distinct ; the posterior is large and 

 fixed to an ear-shaped expansion of the valve at that end : 

 pallets or bars (set in the muscular ring at the base of the 

 pallial tubes) paddle -shaped, with a narrow stalk ; the blades 

 are covered with an epidermis, and are either simple or com- 

 pound: sheath tubular, often nexuous, usually open at both 

 ends, and always at the posterior or outer end, which is 

 conical and has the throat lined with a series of slight con- 

 centric plates. 



Nearly all these burrow in hard vegetable substances ; 

 none in stone. A species allied to Teredo (Kuphus 

 arenarius) , which inhabits tropical seas, lives in sand ; 

 its sheath is closed at the anterior or broader end when 

 the animal has attained its full growth. Deshayes, 

 Quatrefages, and Emile Blanch ard (all eminent physio- 

 logists) consider the Teredinidce a distinct family, on 

 account of their peculiar organization ; according to 

 Gray and the authors of the ' British Mollusca ' thev 

 ought to be comprised in the Pholadidm. The ex- 

 tremely elongated shape of the body, and its being en- 

 veloped in a testaceous sheath or cylinder, as well as 

 possessing a pair of paddle-shaped bars to protect the 

 tubes of the mantle, seem to be characters not less 

 important than those which distinguish any other two 

 allied families of the Conchifera. 



Genus TERE'DO* Sellius. PL IV. f. 4. 



Characters included in those of the family. All our native 

 species have simple pallets. 



1. General remarks. — The "shipworm" of British 



* A borer, from repeat 



G 2 



