LECTURE XL 
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 £A, another at 10, and a 
third at no less than As a species, the Eu- 
ropean pearl-muscle, or more properly 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 
Linnasus attempted to put in practice in Europe, 
of forcing, as it were, the production of pearls, in 
the Mya margaritifera 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 Stromhis gigas or great rose-mouthed Strombus some- 
times produces pearly concretions of a fine rose-colour. 
