Pearl divers. 



CHAPTER IX 



MOLLUSKS 



THE FRESH-WATER MUSSEL 



SUGGESTIONS. The mussel is usually easy to procure from 

 streams and lakes by raking or dredging. In cities the hard- 

 shelled clam, or quahog, is for sale at the markets, and the follow- 

 ing descriptions apply to the anodon, unio, or quahog, with 

 slight changes in regard to the siphons. Mussels can be kept 

 alive for a long time in a. tub with sand in the bottom. Pairs of 

 shells should be at hand for study. 



External Features. The shell is an elongated oval, 

 broader and blunter at one end (Fig. 188). Why does 

 the animal close its shell ? Does it open the shell ? 

 Why ? Does it thrust the foot forward and pull up to it, 

 or thrust the foot back and push ? (Mussels and clams 

 have no bones.) Does it go with the blunt or the more 

 tapering end of the shell forward? (Fig. 188.) Can a 

 mussel swim ? Why, or why not ? 

 H 97 



