12Gf Mr Thompson on the Teredo navalis, 



just received (January 1834), which were alive in their native 

 element a few days ago^ are of equal size to those sent from 

 the same place five years since, when its presence was first disco- 

 vered, shewing that it has not been affected by the cold of the 

 winter season, as we might reasonably expect, were the animal 

 truly exotic. 



By Mr Hyndnian (Member of the Natural History Society 

 of Belfast), I have been favoured with some valves and opercula 

 of the Teredo navalis, which he obtained from the bough of a 

 tree, found imbedded in blue clay twelve feet beneath the sur- 

 face, during the recent excavation of Dunbar's dock in diis town. 

 The greater number of these specimens are small^ but one shell 

 and the valves and opercula of another, or of its fabricator, are 

 as large as any from Portpatrick. The shell of another of these 

 is one-tenth of an inch in thickness. On consideration of the 

 depth at which this tree was found, and the presence of several 

 strata of shells above it and near the surface, I come to the con- 

 clusion that it was deposited in the place of its discovery at a 

 very remote period, not only for centuries before there was any 

 history of the Teredo, but before Europe enjoyed any commerce 

 with either the East or West. 



Though it should be said that we cannot reasonably conjecture 

 what the final destination of a piece of timber containing the Te- 

 redo may be when once committed to the ocean, yet from the 

 fact of its being discovered at Belfast, in the situation just de- 

 scribed, added (without taking other circumstances into conside- 

 ration) to its reaching the magnitude at Portpatrick which it 

 does in India, I am disposed to consider its foreign origin very 

 doubtful. If this animal has been originally introduced, and 

 has been preserved only by occasional importations (See Osier 

 in Phil. Trans.), should we not rather look for it in those ports 

 of the United Kingdom, where vessels from every quarter of the 

 globe are congregated, than in the obscure harbour of Portpa- 

 trick, which has never b3en visited by a foreign craft, and is on- 

 ly used as a secure station for His Majesty's steam-packets that 

 ply thence to Donaghadee. * 



• When visiting the western coast of Ireland in June 1834, accompanied 

 by Robert Ball, Esq. of Dublin, we remarked that nearly all the timber used 

 by the peasantry living near the shore was pierced by the Teredo navalis. This 



