LECTURE XI. 179 



found in rivers in the north of England, in Scot- 

 land, Ireland, and many other parts of Europe. 

 In the seventeenth century several rich pearls of 

 large size are said to have been obtained from this 

 shell in some of the rivers of Ireland. One was 

 valued at upwards of .4, another at . 10, and a 

 third at no less than .40. As a species, the Eu- 

 ropean pearl-muscle, or more properly My a, is 

 distinguished by having a thick, coarse, blackish 

 shell, generally barked or decorticated towards the 

 hinge *. 



I have before mentioned, when speaking of 

 the real or Indian Pearl-Shell, the French art of 

 making artificial pearls. There exists also an art, 

 said to be often practised by the Chinese, and which 

 Linnaeus attempted to put in practice in Europe, 

 of forcing, as it were, the production of pearls, in 

 the Mya mar gar it if era or European pearl Muscle, 

 by piercing the outside of the shell in several 

 places, so as barely not 'to make complete perfo- 



* Pearly concretions are also occasionally formed in all shells, 

 and are of different colours according to that of the shell in which 

 they are formed. Thus, the animal of the large univalve shell 

 called the Strombus gigas or great rose-mouthed Strombus some- 

 times produces pearly concretions of a fine rose-colour. 



