130 POPULAR CONCHOLOOY. 



valve impressions to receive them ; shell thin, 

 and nearly transparent. Animal very little 

 known. — 3 species recent, 1 fossil. 



Pound on sand in India, China, the Red 

 Sea, &c. The Placuna Placentia, commonly 

 known as the Chinese window oyster, is suffi- 

 ciently transparent to be used for windows, 

 lanterns, &c, as horn is used in this country.* 

 Though the animal has not been much ex- 

 amined by naturalists, it is obvious that it 

 must be exceedingly flat; indeed, not much 

 thicker than a shilling ; for the valves, when 

 closed, appear nearly to touch. The shells 

 are sometimes waved, and bent in a curious 

 manner. 



84. Placunanomia (Broderip). — Shell irre- 

 gular, nearly equivalve, smooth, plaited round 

 the edge, and somewhat glossy inside. The 

 hinge consists of two narrow ribs, unequal in 

 length, and converging at the base, in one valve, 



* Mr, Gray mentions that the Chinese use the powder 

 of this shell as silver in their water-colour drawings. He 

 has himself used it in colouring the figures of fish with 

 good effect. It is not quite so brilliant as the powdered 

 leaf metal, but it has the advantage of not changing colour 

 by exposure. 



