6o 



ECONOMIC ZOOLOGY 



which may be a beautiful pure white color within are often used as 

 fonts for holding holy-water in churches. 



In parts of Africa and India cowries or porcelain shells are used 

 as money and the well-known wampum of the American Indians was 

 made from the shells of the quahog, especially those that were lined 

 with blue, and from the colored adductor muscle scars of other lamel- 

 libranchs. 



FIG. 43 A gastropod shell, Murex sp. xM- 



Pearls and Mother-of-pearl. The shells of lamellibranchs are se- 

 creted by the mantle. In most species this secretion is mainly a dull 

 white calcium carbonate, but in some species it is laid down in glossy 

 iridescent layers and is known as mother-of-pearl. If of a fine qual- 

 ity, it may be used for various ornamental purposes; if of a less fine 

 grade it may still be used in the manufacture of pearl buttons. The 

 pearls, which may be attached to the inside of the shell or may be free 

 between the shell and the mantle, are formed by the same glands of the 



