168 MYTILIDiE. 



and timber, in the Commercial Docks, by James Bryant, 

 Esq., who used the animal as bait for perch."" Mr. Stark 

 found it in the Union Canal, near Edinburgh, in ]834, and 

 the Rev. M. J. Berkeley observed it in the Nen, in 1836. 

 In the latter case, the discoverer believed it had been 

 introduced from Wisbeach on timber, in 1828. Thus, it 

 would appear to have found its way into Britain, at several 

 points, and is now common in the canals of the Midland 

 and Northern counties. 



On the Continent it is found in the Wolga, Danube, 

 Elbe, and many of the rivers of Germany and Belgium. 

 It occurs in both the Caspian and Black Seas, and fossil in 

 Transylvania. It is, probably, a species of ancient origin, 

 and one of the members of the old Aralo-Caspian fauna. 



MYTILUS. LiNN^us. 



Shell equivalve, very inequilateral, subtriangular, more 

 or less tumid, surface covered with an epidermis ; beaks 

 terminal. Hinge without true teeth, though often more 

 or less denticulated ; ligament linear internal ; two unequal 

 muscular impressions, pallial impression obscure, simple. 



Animal oblong, its mantle freely open in the branchial 

 and ventral region ; ventral margin simple, branchial fur- 

 nished with pinnated fringes ; anal opening plain and 

 sessile ; adductor muscles unequal ; foot narrow, ligulate, 

 furnished with a byssal groove. 



This genus and the next come so near each other, that 

 many malacologists of repute have given up the idea of 

 drawing a line between them. Until, however, we find 

 that the very important difference between them in the 

 construction of the branchial region of the mantle be proved 

 a specific and not a generic distinction, we feel bound to 



