MYTILUS. 
71 
and ill greatest perfection on the coasts of the 
Persian Gulf and of the Island of Ceylon. The 
term Pearl-oj/s^er is, therefore, incorrectly, though 
commonly, applied to the shells which principally 
produce pearls ; for although they may some- 
times be found in the Ostrea edulis and other spe- 
cies, the Mytilus margaritiferus and the Mya mar- 
garitifera are pre-eminently those from which 
the pearls of commerce are obtained. In the great 
fisheries established to supply the Eastern market^ 
the number of fish annually taken up from their 
beds by divers, whose perilous trade it is to search 
for them, is almost incredible. Some of the shells 
contain one or more pearls ; others, not any. They 
are usually detached, but adhere often to the valves, 
and are extricated by opening the shell and wash- 
ing. After the day’s work, the pearls which have 
dropped out are selected and assorted. The 
small or seed-pearls are worth from three to seven 
guineas per ounce. Those of half a grain weight 
are sold for about eighteen pence or two shillings 
each ; and those of one grain from three to four 
shillings ; of two grains from seven to nine shil- 
lings each ; of five grains from thirty-five to forty- 
