MYTILUS. 71 



and in greatest perfection on the coasts of the 

 Persian Gulf and of the Island of Ceylon. The 

 term Pearl-oyster 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 

 g-uineas 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- 



