84 Pearls. 



upwards ; these lines however are not seen in old 

 shell, as they are soon destroyed by decay. 



Great differences are presented by the appear- 

 ance of the oyster when opened, the outer edge of 

 the *' mantle " being in some cases black, and in others 

 orange, speckled with either black or white spots. 

 In fact the Meleagrince are subject to much local 

 variation, and the appearance of the shell will 

 generally allow a tolerably close conjecture as to 

 whence it came. The black-edged variety is the 

 most distinct both in the oyster and in the shell. 

 In some shells the pallial line is more strongly 

 marked than in others ; in the Sooloo shell, the im- 

 pressions of the adductor muscles are comparatively 

 faint and almost smooth, whilst in the Australian 

 shell a rough, uneven surface is more commonly 

 found. 



Mother-of-Pearl shells vary in weight, when 

 clean and dry, from 400 to 4,000 pairs (/. r., single 

 oysters) to the ton, but occasional specimens have 

 weighed as 'much as 14 lbs. 



The valuable white shell is obtained chiefly 

 from Tahiti and Macassar, the trade port of the 

 Aru Islands, near New Guinea. It seems to exist 

 in close proximity to the other varieties, without 

 losing its distinctive peculiarity, for it is found 

 year after year to the south side of Tapul, an 



