ORDER UXIMUSCULOSA. 77 



Linnaeus, who pierced the shells of the fresh-water mus- 

 sel, causing thereby a pearl to he formed at the punctured 

 spot ; and the Swedish government actually established 

 artificial pearleries, — but these were abandoned after a 

 few years; for, although pearls were formed, they were 

 seldom of sufficient size to be of much value. 



False pearls are made of hollow glass globules, the 

 inside of which is covered with a liquid, called pearl- 

 essence, and then filled with white wax. This liquid is 

 composed of the silver-coloured particles which adhere 

 to the scales of the bleak, (ablette,) and was first applied 

 to this purpose, early in the last century, by a French- 

 man of the name of Jacquin*. 



The Hammer Oyster, {Malleus albus.) 



The singular figure of this shell renders it very remark- 

 able; externally its appearance is very rude and irregu- 

 lar, but, on the other hand, the inner surface is equally 

 beautiful, being covered with the most brilliant mother- 

 of-pearl. The different species of the Malleus are all 

 marine, and found in the seas of hot climates, and the 

 rarity of some causes them to be very valuable, and 

 much sought after. Like the neighbouring genera, the 

 animal is furnished with a byssus, or beard, by which it 

 adheres to the rocks. 



The Rough Pinna, {Pinna rudis.) 

 The Pinna is a marine shell ; most of the species are 

 large, and the shells very thin in proportion to their size. 

 That represented in the engraving is found in the 

 American seas, and is sometimes as much as a foot and 

 a half in length ; it is by no means rare. There is a 

 * See Book of Fishes, p. 51, 



