Mr. W. Thompson on Chelura terebrans. 161 



of June last*. I have therefore only to offer a few remarks 

 bearing on the species as found at Ardrossan. 



Limnoria and Chelura are both present in a piece of wood from 

 Kingstown pier, Dublin bay, given me in 1842 by Mr. R. Ball, 

 as well as in the wood from Ardrossan. 



Both species bore in the direction of the grain of the wood, 

 and their cells are quite alike in character : I perceive no mark 

 of distinction when the animals are of equal breadth. The first 

 piece of wood pierced by the Chelura which I had an opportunity 

 of examining — that from Kingstown — contained the excavations 

 of large adult individuals. The borings of these were so con- 

 siderably larger than those of the Limnoria which had come 

 under my notice, as to lead me to believe that the difference in 

 the size of the aperture would at once distinguish the working 

 of either species. The piece of wood from Ardrossan, however, 

 not only proved that this was no criterion, but — from the circum- 

 stance of the Chelura being small, and less in breadth than the 

 Limnoria — that theirs were rather the smaller cells. 



Both the Crustaceans, like the Teredo and Xylophaga, labour 

 harmoniously together in the work of destruction, and are min- 

 gled in the wood as if they were all of one species. 



They can be readily distinguished from each other either when 

 alive or dead, the Chelura being of a reddish, the Limnoria of a 

 pale grayish yellow hue resembling that of light-coloured pine or 

 fir. As they retain their colours after death, we may even years 

 afterwards distinguish the two species in the excavations which 

 they had formed in timber subjected to their ravages. From this 

 circumstance, added to that of their burrows being formed in the 

 closest contiguity, and many of the creatures dying in them after 

 the timber has been removed from the sea, we may in our museums 

 display whole catacombs of them as closely packed as ever were 

 mummies in the best-tenanted tombs of Egypt. And the Crus- 

 taceans have this advantage, that 



" Each in his narrow cell for ever laid " 



remains perfect as in life, without the aid of any preservative. 



On first learning from my friend Professor Allman that the 

 two species were found associated together, I re-examined — for 

 the purpose of ascertaining whether the Chelura might not have 



* The species (regarding Philippi's as not distinct) was however known 

 to and named by Dr. Leach. British specimens (but from what locality 

 is unknown) belonging to his collection are in the British Museum, and are 

 labelled Nemertes nesceoides, Leach. Under this name they appear in the 

 very carefully and elaborately compiled " List of the specimens of Crustacea 

 in the collection of the British Museum " published this year, the work of 

 Mr. Adam White. The name is I believe unpublished ; at any rate, both 

 Nemertes and Chelura are preoccupied as generic terms. 



Ann. $ Mag. N. Hist. Vol. xx. 12 



