Natural History of Molluscous Animals. 249 
Art. XI. An Introduction to the Natural History of Molluscous 
Animals. Ina Series of Letters. By G. J. 
Letter 4. Benefits. 
Sir, 
So far from having, as you may suppose, estimated too highly 
the use of molluscous animals in the economy of nature, or 
exaggerated their importance to man, I, on the contrary, 
feel persuaded of having understated both; and it would have 
been easy for a naturalist, more favourably situated for in- 
vestigation, to have made out a much “ stronger case.” Your 
future studies will soon convince you of this ; and, in the mean 
time, the additional facts about to be detailed will prove that 
I have by no means exhausted my subject. To proceed. 
Pearls are not, as poets have feigned, 
“ rain from the sky, 
Which turns into pearls as it falls in the sea,” 
but they are the morbid secretions of an oyster. Several 
species of bivalved shellfish produce them, but the greater 
number, the finest and the largest, are procured from the 
Meleagrina margaritifera Lamarck ( fie. 44. a), a native of 
fo) oO fo) ’ 
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the sea, and of various coasts. A considerable number are 
likewise taken from the U’nio margaritifera (b), which inha- 
bits the rivers of Europe; and it is singular, as remarked 
by Humboldt *, that though several species of this genus 
abound in the rivers of South America no pearls are ever found 
in them 
The pearls are situated cither in the body of the oyster, or 
* Personal Narrative, vol. ii. p. 282. 
Vor, blll, —— No. 13; s 
