70 PIIOLADID^. 



ventral edge is very solid, and uot broad. The tube is 

 long, slender, tapering, and flexuous, divided at the narrow 

 end by thin, close-set, transverse, circular partitions, ten or 

 twelve in number, which do not occupy the entire area, but 

 leave a large oval orifice in the middle ; the posterior aper- 

 ture is contracted in the middle. The pallets, or caudal 

 appendages, are somewhat spoon-shaped, being convex on 

 one side, and concave on the other ; a rib-like elevation 

 running down the centre of the latter projects above it, and 

 forms a slender, cylindrical, and oftentimes flexuous handle 

 opposite to the straightish or slightly convex base. 



The length of the valves in our British or Irish speci- 

 mens rarely exceeds half, and the breadth four-sevenths of 

 an inch ; and tubes exceeding a foot in length are very 

 seldom, if ever, to be met with in our cabinets. 



The opinion appears to be prevalent among British natu- 

 ralists, that the Teredo norvagica was originally of foreign 

 importation, and that, although decidedly naturalised for a 

 season in the harbours of Plymouth and Falmouth, it has 

 at length, through the strenuous exertions of government, 

 become entirely extirpated. Mr. Osier, in the " Philoso- 

 phical Transactions^' for 1826, remarks, that in the above- 

 mentioned harbours, wdiere it was once so perniciously 

 abundant, it is now no longer to be found ; and at Devon- 

 port the few specimens long ago extracted from one of the 

 piles, are now, from its utter extinction, treasured and 

 exhibited as curiosities. Several of our earlier writers, in- 

 deed, (Pulteney, Da Costa, &c.,) only knew it as obtained 

 from foreign timbers, and consequently regarded it as a 

 doubtful native, and Pennant, who first introduced it into 

 systematic Conchology as an inhabitant of Great Britain, 

 defined it by neither figure nor description. Montagu, 

 however, who described tlie characters from naturalised 



