TYPICAL BIVALVES. 229 
grooved, with a gland for secreting a bundle of threads, the 
byssus, by means of which it is anchored to the bottom. 
ols 
Fie. 163, hig. 164. 
Fig. 163.—Mytilus edulis, common mussel, with its fringe expanded, and an- 
chored by its byssus.—After Morse. 
Fig. 164.—Cyclocardia novanglie, natural size.—After Morse. 
The foot in the quohog (Fig. 165 A, Venus mercenaria), 
Mulinia (166 B) and Clidiophora (Fig. 167) is large, these 
Fig. 165 4.—Venus mercenaria, quohog, natural size, with the foot and siphons. 
Fig. 166 B.—Mactra (Mulinia) lateralis, natural size.—After Verrill. 
mollusks being very active in their movements. In Glyci- 
meris (Fig. 168) the fringe is toothless, much as in the 
oyster. In Mactra (Fig. 169) the middle tooth is large, the 
