COMMON FKESHWATER SHELLS. 245 



century, especially in the river Tscy, where the peasants collected 

 them before harvest time. The pearls were usually found in old 

 and deformed specimens. Round pearls, perfect in every respect, 

 about the size of a pea, were worth from three to four pounds. 



In the Irish Pearl Fishery the mussels are said to have been 

 found "set up in the sand of the river beds with their open side 

 turned from the torrent." About one mussel " in a hundred 

 might contain a pearl, and one pearl in a hundred might be 

 tolerably clear." So that one mussel in every ten thousand which 

 were opened might contain a tolerably clear pearl. At one time 

 the pearl fisheries in this country were a source of considerable 

 revenue to their owners. It is stated in Brown's Receiit Conchology 

 that the pearls sent from the river Tay, in Perthshire, to London 

 from the year 1761 to 1764 were worth ;^io,ooo. Tradition is 

 silent as to how many mussels were killed in this search for pearls, 

 but the number must have attained coUosal dimensions. 



It may be mentioned in passing that Unio mai'-garitifer is 

 mythologically supposed to have furnished pearls for the British 

 crown. One pearl furnished by this mussel, seen by Sir R. 

 Redding (who lived in the seventeenth century) was purchased for 

 ;^3o by the owner, who had previously refused nearly three times 

 that sum for it. 



British pearls, by the way, have played a part in Classic His- 

 tory. It is mentioned by Pliny that Julius Caesar obtained in 

 Britain a sufficient number of pearls to cover a breastplate, which 

 he dedicated to Venus and hung in her temple. It is evident from 

 Pliny's account that the pearls were small and comparatively value- 

 less, and so Caesar's piety has been treated with incredulity, and 

 the suggestion offered that he only presented the pearls to the 

 goddess because the Roman ladies would not have worn them. 

 These pearls may have been produced by Unio margaritifer or by 

 the common edible mussel. 



Pliny also furnishes us with another classical piece of con- 

 chology, the truth of which is not borne out by modern investiga- 

 tions. Here, however, he is apparently not speaking of freshwater 

 shells. He tells us that the divers had to practice considerable 

 skill, for the oyster snapped at the diver's fingers and lopped them 

 off if he vyere not quick enough in his motions. 



