THE CLAM AND OTHER BIVALVED SHELL-FISH. 63 



three teeth in the right and two in the left valve, while the 

 hinge-margin is very solid. We also see the muscular im- 

 pressions, which are connected by the "pallial line/' The 

 edge of each valve is purple. This part of the shell was 



Siphon 



FIG. 63. Unto, or fresh-water mussel, with its large foot partly buried in the 

 sand, the siphonal openings above the level of the river-bottom. 



used by the Indians in making beads for money, or " wam- 

 pum." 



The inland student who cannot readily obtain live sea- 

 clams should pick up the mussels from the edge of ponds 

 and rivers, carry them home, put them into pans of water, 



FIG. 64. Mytilus edulis, common mussel, with its siphons expanded, and an- 

 chored by its byssus. 



with plenty of sand on the bottom, and then after a while 

 watch their motions. 



The mussel will be seen to thrust its large foot out, dig 

 and burrow into the sand, until it buries itself out of sight. 



