TEREDO. 157 



lent that the Teredo had been originally introduced into 

 Europe from foreign parts — " calamitas naviuni ex In- 

 diis in Europam propagata," Linne, — which seemed to 

 be in some measure confirmed by its sudden appearance 

 in particular years. Even Mr. Osier, so late as 1826, 

 took for granted that T. Norvegica was not a native of 

 the British seas ; and he expressed his belief that, until 

 the general use of copper sheathing, it was probably 

 preserved only by occasional importations. But we now 

 find that each kind of Teredo has its own special area of 

 habitat. Tropical species will not live in the temperate 

 zone, and vice versa. That the Teredo is not of modern 

 origin in Europe is evident from the fact that T. Nor- 

 vegica, which at present is distributed over the North 

 Atlantic from Einmark to Sicily and Algiers, is also 

 found in both old and new deposits of our upper Tertiary 

 formation. T. megotara inhabits the coasts of Shetland, 

 and more northern latitudes in both hemispheres ; and 

 it occurs in a fossil state at Belfast and Uddevalla. 

 Deshayes first noticed the same fact with regard to T. 

 Norvegica being a fossil of the Italian tertiaries, as well 

 as of the Crag ; and it appears to be conclusive. 



7. Distribution in the British seas. — Its distribution 

 along the British coast appears to be somewhat capri- 

 cious. Seaports, in which the admixture of fresh water 

 is considerable, such as Hull and Liverpool, are exempt 

 from the Teredo. But this rule has its exceptions. 

 The Medway is infested with the Dutch ship worm (T. 

 navalis), especially the upper reaches of the river, where 

 the water becomes less salt. I extracted living speci- 

 mens from the keel of a " watch boat/' kept at anchor 

 off Queensborough in that river for the purposes of the 

 lobster trade in the Billingsgate market. Milford 

 Haven has the Norway shipworm (T. Norvegica) 



