io6 



BUI,LETIN OF THE BUREAU OF FISHERIES. 



Table 6. — Habitats op Certain Fresh-water Mussels, Classified According to Character 



OF Bottom. 



It appears from this and the following table that the preferred bottom for the 

 majority of species is mud (but not deep, soft mud, to which type of bottom few species 

 are adapted) and gravel, including sand and gravel. Sand ranks next and clay last; 

 but few species of mussels exhibit a preference for sand or sandy clay, and only two are 



