354 
CHAPTER XII. 
ACEPHALOUS MOLLUSCA—(continued). 
MYTILIDZ—THE MUSSEL FAMILY. 
“ Ecce inter virides jactatur mytilus algas.” —Anthologia. 
WE now come to consider the nineteenth family, that of Mytilide, 
which includes the genera called Mytilus, Modiola, Lithodomus, and 
Dreissena. 
The well-known shell of the mussel (AZptilus edulis, Fig. 156) is 
Fig. 156.—Mytilus edulis (Linnzeus). 
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 Afytilus 
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 Léthodomus the byssus is rudimentary. In Dretssena 
the shell is like that met with in the genus AZyd/us, but without its 
pearly lining. 
The animal of Afyiilus edulis, as described by M. Chenu, is 
