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GENERAL ZOOLOGY 



The Fresh- Water Mussel 



Habitat and Distribution. In fresh waters generally, wher- 

 ever sufficient carbonate of lime is carried in solution, one 

 may find mussels living nearly covered in sand and mud. 

 The species represented in Fig. 107, Ellip'tio complana'tus, 

 is distributed in the rivers and brooks of the Atlantic states. 



Fig. 107. Living fresh-water mussel, (x \) 



Comparison with Other Forms. The valves of the mussel 

 are equal, like those of the clam and the scallop. The valves 

 of the fresh-water species are held together by a hinge lig- 

 ament, aided by two pearl-covered ridges running parallel 

 and fitting into grooves. The mantle folds are not united 

 as they are in the clam. The siphons are here merely open- 

 ings between the two mantle lobes, not a protruding tube 

 as in the clam. At two adjoining places in the posterior 

 region the rim of the mantle folds is fringed with short ten- 

 tacles. Dorsal and ventral openings, or siphons, are formed 

 by the meeting of opposite edges at the places where the 



