58 pholadidjE. 



TEREDO, Adanson. 



Shell globular or annular, regular, composed of two equal 

 much-curved polygonal valves, their outer surfaces striated 

 in various directions, the inner surface presenting only one 

 distinct muscular impression. No true hinge ; ligament ob- 

 solete ; a curved process beneath the beaks of each valve. 

 No accessory valves at the back of the shell. 



Animal vermiform ; mantle tubular, slightly open ante- 

 riorly; siphons very long, bifurcating at their extremities, 

 orifices fringed ; a muscular ring, into which are inserted 

 two variously shaped calcareous ossicles (pallets), at the 

 part where the siphons divide; branchise continued into the 

 siphonal tube; foot rudimentary, sucker-shaped. 



Tube calcareous, cylindrical, lining the cell in which the 

 animal is lodged. 



The genus Teredo is the most abnormal of all the lamel- 

 libranchiate bivalves ; nor is it to be wondered at that the 

 ancients, and the older writers among the moderns, regarded 

 it as a worm rather than as a mollusk. The resemblance 

 of its tube to that constructed by the Serpula^ and the 

 worm-shaped body of the creature itself, naturally sug- 

 gested the notion that it was an annellid, while even the 

 valves of the shell seemed rather like the jaws of some cu- 

 rious and voracious worm, which, by means of them, eat 

 its way into the planks of ships and piles of harbours, than 

 like the shells familiar to casual observers. The powers 

 of the creature to do mischief aided the prevalent fancy ; 

 and the terror which its ravages seem in all ages to have 

 inspired, blinded the half-instructed naturalists, who cu- 

 riously examined it, to its true affinities. 



The researches of anatomists during the last and present 



