DREISSENA. 167 



ami the coloured markings woukl appear from Oaptaiu 

 Erown"'s figures to be occasionally obsolete. That gentle- 

 man observes, that the scars in his specimens were of a 

 purple hue ; this, however, is not the case in our ex- 

 amples. 



The animal has the mantle closed in front, except a 

 small opening, from whence the short ligulate, or subcy- 

 lindrical foot can be protruded, when it desires to fix its 

 byssus. This portion of the mantle is white, and the mar- 

 gins of the orifice are simple. At the posterior or wide 

 extremity, the mantle becomes of a yellowish or fawn 

 colour, striped in a zebra-like manner with dark brown or 

 purple ; it is there prolonged into a cylindrical tube, with 

 a circular orifice, which is bordered and internally fringed 

 by short rather stout pointed cirrhi. Above this dorsally, 

 at a little distance, is the slightly projecting and much 

 smaller anal orifice, similarly coloured, but not fringed. 

 The animal pouts out both orifices freely in confinement. 

 The foot is white, except its byssiferous grooved portion, 

 which is of a pale yellow colour. The lips are rather large, 

 triangular, and lanceolate. 



These mussels live gregarious, often attached in great 

 numbers to each other, in fresh and brackish waters. 

 Originally, apparently, inhabitants of the rivers around the 

 Black Sea, they have gradually extended their range all 

 over Europe ; capable of enduring salt-water for a time, 

 they have, probably, been carried across seas on the 

 bottoms of ships, and in this manner have reached Eng- 

 land and become so common in our canals, as to be much 

 more abundant than many of our indigenous mollusks. Its 

 history, as a British species, dates from 1824, when Mr. 

 J. de Carle Sowerby exhibited it to the Linnean Society, 

 stating that it was found " in abundance, attached to shells 



