1883. ] Pearls and Pearl Fisheries. 581 
For technical purposes pearl-producing mollusks are divisible 
into two classes, fresh-water and marine. It is noticeable that of 
all the great multitude of air-breathing snails which live upon 
land, or in trees, not one produces a nacreous shell; and, further, 
that even among fresh-water mollusks none of the air breathers 
are pearly, and few of those which breathe by gills, except part 
of the bivalves, especially those belonging to the group typified 
by our common river mussels, and so appropriately called the 
Naiades, We will first consider these, of which the most import- 
ant is the true European pearl mussel (Margaritana margari- 
tifera L). 
This mollusk is found in cool temperate climates over most 
parts of the northern hemisphere, though not plenty in America 
and somewhat irregularly distributed. It requires clear streams 
or ponds, of which the water contains a certain proportion of lime. 
These conditions are fulfilled in several parts of Britain, North 
Wales, Sweden, France and Germany, Russia and Siberia. The 
use and value of these pearls were known to the ancient Romans 
at a very early period. One reason for the invasion of Britain is 
said to have been the reputed pearl fisheries. Pliny remarks that 
it was in his time a well-known fact that “in Britannia pearls are 
found, though small and of poor color; for Julius Cæsar wished 
it to be distinctly understood that the breastplate which he pre- 
sented to Venus Genetrix in her temple, was made of British 
Pearls.” Tacitus mentions them as indigenous produets of Bri- 
tain in his life of Agricola, describing them as paler and less 
brilliant than oriental (marine) pearls. The search for pearls, a 
Profitable industry in which the ancient Britons eagerly engaged, 
'S still carried on to some extent in Wales. The traveler who 
Sojourns in the vicinity of Conway castle is sure to be solicited to 
buy some British pearls, which in 1857 were worth from one to 
three dollars an ounce, but are chiefly valuable as curiosities.’ 
‘Dout one mussel in a thousand contains a pearl large enough to » 
be of any value, so that it is evidently not a very remunerative 
Pursuit, 
The British pearl fishery is fully described by Forbes and Han- 
in their British Mollusca. The Conway and the Irt in Eng- 
land, the Tay and Yythan in Scotland and the rivers of Tyrone 
and Donegal in Ireland were the site of the principal fisheries. 
1 ‘ 
Encycl, Brit., Ed. vir, Art. Pearls, 
