14 PEARLS [CH. 



Of the many other species^ of Margaritifera it 

 will perhaps suffice to mention the " Sharks Bay 

 shell," which is fished at Sharks Bay, Western Australia, 

 and plays an important part in the button industry. 



Fresh-water molluscs in which pearls are found 

 include many famous species belonging to the family 

 Unionidae in the rivers of the British Islands. 

 Margai'itaua Qnargariti/era, Linne, occurs in the 

 rivers of Scotland, northern England, Wales, and 

 the mountainous parts of Ireland. 



It is from this shell that the valuable fresh-water 

 pearls have been obtained. The shell is thick, and is 

 oblong in shape with both ends obtusely rounded. 

 The surface is rough and dark brown in appearance. 

 It is between five and six inches long. 



The Romans came to Britain for the Unio pearls 

 and there is some evidence to show that they fished 

 the Welsh rivers for them. Many valuable pearls 

 have also been taken from TJjiio in Scotland, and 

 an important Scotch pearl fishery was once in 

 existence on the Tay in Perthshire. The Irish pearl 

 mussels seem to have decreased in number — perhaps 

 owing to the wanton destruction which has occurred 

 owing to the search for pearls. Pearl mussels occur 

 in the rivers of Central Europe, and America (both 

 Canada and the United States). 



1 For a complete list reference should be made to Jameson, Proc. 

 Zool. Soc, 1901. 



