CHELURA AND LIMNORIA. 305 



creatures, which resemble minute Wood-lice, or Shrimps, 

 attack, like the Teredo, any submerged wood-work, and 

 rapidly perforate it in all directions, till it is reduced 

 to a mere shell, ready to fall to pieees on the slightest 

 touch. The Limnoria, which is the larger of the two, 

 bores directly into the timber, piercing deeply nearly 

 at right angles with the surface ; while the Chelura 

 excavates obliquely, rather ploughing up the surface 

 than forming a deep burrow. Its work of destruction 

 proceeds with fearful rapidity, particularly where it 

 follows, as is often the case, its friend, the Limnoria. 

 The loosened surface is rapidly washed away by the 

 action of the water, and a new one exposed, to be in 

 turn ploughed over by the busy creature. Though the 

 means in action seem small, if we regard merely the 

 size of these destructive insects, yet, when countless 

 multitudes establish themselves in a beam, the untiring 

 play of their jaws soon reduces the most solid timber to 

 powder. Nor is it only constantly-submerged timber 

 which suffers from them. They can endure to be left 

 dry at low water, and the Limnoria has been kept 

 alive for a considerable time in its burrow by merely 

 an occasional moistening of salt and water. * 



Among the objects which occasionally float ashore, or 

 drift about with the waves, are dark- coloured, roundish, 

 or spindle-shaped bodies, of the size and colour of grapes, 



* Kirby and Spence, vol. i. p. 204, in note (6th edit.). An excel- 

 lent account of the Limnoria has been published by Dr. Coldstream, 

 in firewater's Journal ; and Professor Allman has given us a most 

 elaborate paper on Chelura, in which the structure of the animal is 

 very fully detailed, in the Annals of Natural History, vol. xix. p. 361. 



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