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CHAPTER XII. 



ACEPHALOUS MOLLUSCA—icofi/lnued). 



MYTILID^E — THE MUSSEL FAMILY. 



" Ecce inter virides jactatur mytilus algas." — Anthologia. 



We now come to consider the nineteenth family, that of Mytilidse, 

 which includes the genera called Mytilus, Modiola, Lithodomus, and 

 Dreissena. 



The well-known shell of the mussel {Mytilus ediilis, Fig. 156) is 



Fig. 156, — Mytilus edulis (Linnaeus). 



longitudinal, equivalve, and regular, pointed at the base, with 

 capacity to attach itself by a byssus ; the hinge has no teeth, but a 

 deep furrow, in which the ligament is located. In tlie genus Mytilus 

 the byssus is strong and coarse, and the palpi are long. In Modiola 

 it is ample, but fine, and the palpi are triangular. In both these 

 genera the foot is elongated and grooved, its retractile muscles 

 numerous. In LitJiodomus the byssus is rudimentary. In Dreissena 

 the shell is like that met with in the genus Mytilus, but without its 

 pearly lining. 



The animal of Mytilus edulis, as described by M. Chenu, is 



