COXCHIFERA. 261 



The cause of their alarm over, they bring themselves 

 to an anchor. When many hundreds of these curious 

 bivalves are seen together in the recesses of clear 

 pools, surrounded by living branches of parti-coloured 

 corals, their crimson-spotted mantles and the fringes 

 around them exhibit a very rich and beautiful 

 spectacle. 



The Scallops {Peden) generally attach themselves 

 to rocks, and sometimes cover extensive banks. 



These bivalves are said to be able to see, and cer- 

 tain bright spots upon the margin of their mantle 

 are believed to be eyes ; indeed, one species has been 

 named, after Juno's watchman, the Argus. Whether 

 these brilliant pearl -like specks, so strangely situated, 

 are really instruments of vision is, however, open to 

 doubt. 



The Pearl-shells {Avicula). To this family belongs 

 the celebrated Pearl-Oyster. Their shells are im- 

 ported in immense quantities, forming the celebrated 

 " Mother of Pearl " so much employed in inlaying 

 cabinet-work, making knife-handles, paper-cutters, 

 and a thousand other pretty articles. 



The Pearl-lishery is principally carried on in the 

 jieighbourhood of Ceylon and in the Persian Gulf. 



