PEARL MUSCLE. 369 



About the year 1730, the Republic of Holland was thrown into 

 a general alarm by the appearance of a vast multitude of these 

 worms on the coast ; and a very extensive depredation which they 

 commenced on the wood work of the dykes, threatening a total de- 

 struction to the republic. Fortunately they disappeared in a few 

 years, perhaps in consequence of the climate being too cold for 

 them. 



[Adanson. Phil, Trans. 1739. Editor. 



Of the Bivalve testaceous worms, or those possessing a shell 

 composed of two divisions, the most common examples perhaps are 

 the oyster (ostrea,) the cockle (cardium,) and the muscle (mytilus.) 

 Among the more curious or extraordinary we may mention the pearl- 

 muscle, the chama, or great clamp. shell, and the pinna. 



1. Pearl Muscle, or Mother .of '.Pearl Shell. 

 Mytilus margaritiferus. Linn. 

 This shell, which grows to a very considerable size, is of a flat- 

 tened and rounded shape, with the back or hinge part strait. Its 

 colour on the outside is brown, variously spotted and clouded ac- 

 cording to circumstances ; and on the inside, as every one knows, of 

 the most brilliant, iridescent, silver lustre. It is a shell of very con- 

 siderable thickness ; and when properly cut and polished is the beau- 

 ful substance usually known by the name of mother-of-pearl, and 

 of which so many ornamental articles are formed ; and from the 

 cartilaginous or tendinous hinge at the back part of the shell, in a pe- 

 trified state, is produced that very rare and beautiful extraneous fossil, 

 called tli Androdamas, (the Helmintholithns Androdamas of Lin- 

 naeus,) which when cut and polished, in the disposition of its fibres, 

 and in its colours, bears some resemblance to the eye of a peacock's 

 feather. But the far more valuable products of this shell are pearls 

 themselves, which are found sometimes loose, and sometimes adher- 

 ing to the shell, as well as in the body of the apimal. 



The pearl muscle, or Mytilus margaritiferus, is most common 

 about the shores of the East-Indian islands ; and particularly at 

 Ceylon, where the chief pearl-fisheries have long been established, 

 and of which an interesting description may be found in the Asiatic 

 Researches, and other publications. According to the tenor of these 

 accounts, one of the chief pearl-fisheries of Ceylon is carried on, at 

 vol. v. 2 b 



