122 Mr Thompson on the Teredo navalis 



From such authors as describe the size of the Teredo navalis, 

 I make the following extracts. In the Ency. Brit, and Rees's 

 Cyclopaedia, it is stated, that " this creature is wonderfully mi- 

 nute when newly exckided from the egg, that its utmost bigness 

 is a foot long : three or four inches is, liowever, its more frequent 

 length." Linnaeus, and after him Gmelin, in his edition of the 

 Sijstema Naturce, remarks, that the shell of the Teredo navalis 

 is from four to six inches in length : this is also the size assigned 

 to it by Matten and Rackett (Linn. Trans, v. 8), who, however, 

 add, " vel majis longa." Dillwyn (Desc. Cat. of Rec. Shells) 

 observes, that it is " sometimes a foot long, and about three- 

 fourths of an inch in diameter at the lower extremity, from which 

 it tapers slightly to the summit ; but the shell in these cHmates 

 is rarely more than half so large." Home (Phil. Trans. 1806) 

 informs us, that of a number of these animals sent him from 

 Sheerness, the largest was in length eight inches. Montagu 

 (Test- Brit.) says, " this part [the testaceous tube] is rarely 

 above three-fourths of an inch in diameter at the larger end, and 

 a foot in length in our climate ; but exceeds that in the more 

 southern parts." Baxter, in a paper communicated to the Royal 

 Society of London (Phil. Trans. 1739-40, parti), "On the 

 Worms which destroy the piles on the coasts of Holland and 

 Zealand," ascribes thirteen or fourteen inches as their greatest 

 length. Denovan (Brit. Shells) states, that he has " seen one 

 of them whose progress through the solid plank had not been 

 interrupted, that had grown nearly to the length of eighteen 

 inches;" and Turton, in his Conchological Dictionary, describes 

 the tube as being " from a foot to two feet in length ;" but nei- 

 ther he nor Denovan informs us whether they were British or 

 foreign specimens that attained the greatest magnitude which he 

 mentions. 



In addition to what is just quoted concerning the general size 

 of the Teredo, it may be added, that the current opinion of au- 

 thors is, that the dimensions of the animal is much greater in the 

 warmer regions of the east, than in the comparatively temperate 

 climate of Europe. The specimens, however, received from the 

 northern locality of Portpatrick at various times, equal, if not 

 surpass, in magnitude the largest as yet stated to have been met 

 with in the Indian Ocean, having almost attained the length of 



