3S4 



CHAPTER XII. 



ACEPHALOUS MOLLUSCA (continued}. 



MYTILID^E THE MUSSEL FAMILY. 

 " Ecce inter virides jactatur mytilus d%p&,"Attthologia. 



WE now come to consider the nineteenth family, that of Mytilidae, 

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

 Dreissena. 



The well-known shell of the mussel (Mytilus edulis, 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 the 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 Lithodomus the byssus is rudimentary. In Dreisscjia 

 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 



