MUSSELS. 195 



ordinary number of 220,000 eggs during the months of May, 

 June, and July. The shells of this bivalve in former days 

 were used for the purpose of holding the painter's colours; 

 hence its specific name. At the present time they may be 

 purchased contaiuiag gold and silver leaf. 



Unio mm-garitifer is especially the " pearl-bearing " mussel, 

 as its specific name implies. It is chiefly found in the rivers 

 of the mountainous districts of Britain. Beautiful and valu- 

 able pearls have at various times been found in this and 

 other species of the UnionidoB. Mr. Oholmondeley Pennell, 

 in his book on " Pike and other Coarse Fish," mentions a boy 

 who, while fishing for trout in the Chapel Brook, near Tweed 

 Mill, Coldstream, caught a large Mussel (the species is not 

 given) which contained no less than "forty fine pearls of 

 different sizes, some of which were thought to be worth ten 

 shillings each." 



The body of U. ma/rgaritifer is a dirty grey, and its foot is 

 large, tongue-shaped, and reddish-brown. The shell is about 

 4in. long and 2in. high, oblong, compressed, and of a darker 

 colour than the rest of the Vnionidae. The umbones, which 

 are more often eroded in this species than in any other of 

 the genus, are placed towards the anterior extremity, which 

 is fairly evenly rounded. The posterior side slopes away from 

 the dorsal margin. The ventral margin is almost straight, the 

 ligament is very long, and the lunula is inconspicuous. The 

 muscular and palHal scars are very distinct. 



The Anodontce are the largest of our fresh-water bivalves, 

 sometimes measuring as much as Sin. in length and Sin. in 

 height, and they should not, therefore, be introduced into a 

 tank imless it is very large and the sand and gravel at its 

 bottom are deep in proportion. 



Anodonta cygnea (Pig. 129) is the only species of the genus 

 which is found in Britain. Various varieties have often 

 been taken for different species, but I think now it is 

 generally considered that there is only this solitary species. 

 The body of the animal is greyish, slightly tinged with yeUow 

 or red. The foot is broad, and of a dirty yellow colour. The 

 shell is oblong, thin, yeUowish-green, or sometimes rusty 



o 2 



