162 Mr. W. Thompson on Chelura terebrans. 



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, Do- 

 naghadee, and Belfast bay : from the first-named places obtained 

 in 1834, 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 admix- 

 ture 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 re- 

 gret to state is not the case. For the purpose of testing this, I 

 requested my friend Edmund Getty, Esq. — who is officially con- 

 nected with the harbour — to have all the beacons or " perches " 

 marking the channel of the river (which they do for about two 

 miles at the upper part of the estuary) examined, and if they 

 proved to be injured, to favour me with specimens of the damaged 

 wood. All this he kindly had done in the month of May last, 

 when the beacons proved to have been all attacked, and those 

 most under the influence of the fresh-water to have suffered 

 equally with those nearest to the open sea. The ship-carpenter 

 who cut the damaged portions off that were sent me, stated to 

 my friend that some old mooring-buoys so high up as the Old 

 Long Bridge were found on removal injured in the same man- 

 ner. The Limnoria was the only borer of any kind found in the 

 beacons alluded to. 



It must be mentioned, that judging from the superior size of 

 the Chelura borings to those of the Limnoria in Dublin bay, I had 

 from that circumstance noted down the perforations in pieces of 

 oak and black birch washed ashore at Belfast as the work of the 

 Limnoria; but perceiving, on examination of the wood from 

 Ardrossan, that the borings of the two species may not only be of 

 equal size, but that those of the latter species may be the larger, 

 I was taught that the presence of the Excavator himself must be 

 essential to settle the point, and that circumstantial evidence is 

 insufficient. The wood in question had been so long tossed about 

 in the sea that the animals were all washed out : — both pieces 

 had also been bored by the Teredo norvegica (T. navalis, Turt.). 



In reference to the length of time that the Chelura will live 

 after being removed from its native element, the following note 

 was made. A few specimens taken from the sea on Monday 

 morning and received by me in the afternoon of that day were 

 alive on Thursday morning, or seventy-two hours afterwards, 

 when, leaving home for England, I took the piece of wood con- 

 taining them with me, and on examining it next day found them 

 dead ; they had probably lived out of their native element about 

 ninety hours. A number had lived in the same wood for about 



