CHAP. XVIII. 



BIVALVES: 

 MYTILUS; Muscle. 



Q. WHAT are the distinguishing characteristics 

 of a Mytilus. 



A. A rough shell, often affixed by a thick 

 byssus or silky beard, to rocks or floating sub- 

 stances. A toothless hinge, distinctly marked, 

 except in a few instances, with a subulate line 

 (having a half-crescent form), excavated longitu- 

 dinally. 



Q. Are not the finest pearls produced by this 

 kind of shell-fish ? 



A, Yes, they are. The pearl-bearing shell 

 of the Indian fisheries is the Mytilus Margariti- 

 ferus : it is most abundant and in greatest per- 

 fection on the coasts of the Persian Gulf and of 

 the Island of Ceylon. The term pearl-oyster is, 

 therefore, incorrectly though commonly applied 

 to the shells which principally produce pearls, 

 for although they may be sometimes found in 

 other species, the Mytilus Margaritiferus and 

 the Mya Margaritifera, are pre-eminently those 

 from which the pearls of commerce are obtained. 

 D 3 



