AMPITIPODA AND ISOPODA OF THE FIPTII OF CLYDE. 81 



Mr. Couch ; the coast of Durham, Rev. A. M. Norman ; 

 and Berwick Bay, the late Dr. Johnston. 



Genus A sell us, Geoffrey. 



ASELLUS AQUATICUS, Lin ne\ 



Oniscus aquations, Linne, Sys. Nat., ii., p. 1061. 

 Cymothoa aquatica, Fahricius, Ent. Sys., ii., p. 505. 

 L'Aselle, Geoffrey, Ins. Paris., ii., p. 672, t. 22, f. 2. 

 A sell-us aquaticus, Olivier, Enc. Meth., iv., p. 252. 

 Habitat. — Common everywhere among the marginal 

 vegetation of ponds, canals, and slow-running streams. 



Genus Limnoria, Leach. 



LIMNORIA LIGNORUM, Rathke. 



Cymothoa lignorum, Rathke, Skrivt. af Naturh. 

 Selsk., vol. 101 ' (1799), t, 3, f. 14. 



Limnoria lignorum, White, Pop. Hist. Brit. Crust., 

 p. 227, pi. 12, f. 5. 



Limnoria terebrans, Leach, Diet, des Sci. Nat., art. 

 Cymothoadees ; Edin. Encyc, vii., p. 433. 



Habitat. — Abundant in the piles of Millport Pier. 

 This little creature is one of the most destructive 

 animals to marine submerged timber. It is very 

 small, measuring not more than \ inch in length, 

 and less than one-half that in breadth, yet in a 

 very short time a number of them will destroy 

 the whole timber of a pier. It appears that these 

 animals, whether from choice of material or facili- 

 ties in working, are partial to particular layers of 

 the w^ood, which they remove with such economy 

 that the divisional walls are barely left standing. 

 In completing this part of their work of destruc- 

 tion, they indiscriminately drive their burrows in 

 all directions. The only time when their operations 

 show a tendency to order is when they enter the 

 solid w r ood ; then in general they cut either obliquely 

 upwards or obliquely downwards. Yet though they 

 seem to be in a great measure guided in the direc- 

 tion of their course by the layers of the wood, they 

 evidently endeavour to avoid cutting through or 



