398 CRUSTACEA. 



Genus Chelura. 

 C. terehrans, Philippi. 



All that has been published on this species has already appeared in the 

 Annals ; Philippi's paper, in which it was first described, having been 

 translated and republished in the fourth volume ; and Professor Allman's, 

 introducing it as an inhabitant of the British seas, having a place in the 

 number for the month of June, 1847. I have therefore only to offer a few 

 remarks bearing on the species as found at Ardrossan. 



Limuon'a and Chelura are both present in a piece of woocl from Kings- 

 town Pier, Dublin Bay, given me in 1842 by Dr. 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 

 Clielura which I had an opportunity of examining — that from Kings- 

 town — contained the excavations of large adult individuals. The borings 

 of these were so considerably 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 Avood from Ardi'ossan, however, not only proved 

 that this was no criterion, but — from the circumstance of the ChelurcB 

 being small, and less in breadth than the Limnoria — that theirs were 

 rather the smaller cells. 



Both the Crustaceans, like the Teredo and XyJophaga, labour harmoni-- 

 ously together in the work of destruction, and are mingled 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 greyish yel- 

 low 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 Avhich 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 

 Crustaceans have this advantage, that 



"Each in liis 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 been overlooked — all 

 the wood that I had preserved on account of Limnoria borings, but in 

 none of it was the former species to be detected. This wood was all pine, 

 and from Portpatrick, Donaghadee, and Belfast Bay : from the first- 

 named places obtained in iy.'54, and from the last in the present year. In 

 the more marine parts of this bay I was not surprised to find that the 

 Limnoria existed. I had however hoped, that where the admixture of 

 fresh with sea-water (if such take place) should be very great even at 

 full-tide, and where at low-water the former only prevails, wood-work 

 would be free from its attacks, but such I regret to state is not the case. 

 For the purpose of testing this, I requested my friend Edmund Getty, 



