156 Colic (jc of Forcslry 



off with varying rapidity into marly sand, then into sandy 

 dark marl that covers the bottom in all the deeper parts of the 

 lake." The mussel zone was found to extend, as a rule, to 

 where the bottom changed to very soft marl, averaging from 

 four inches to nine feet deep ; in some places the mud comes 

 to within a few feet of the water's edge, while in others the 

 sand and gravel bottom extends to water 22 feet deep. 

 Anodonta grandis was found at the outer edge of the sand 

 and gravel area, while Strophitus edentulus occurred a little 

 farther out. Grandis sometimes occurred on a sandy bottom, 

 but edent'ulus was always found on a soft bottom. Neither 

 was ever found on hard sand or gravel. Latnpsilis hiteola 

 was the most variable mussel and also the most abundant in 

 the lake. It exhibited two color phases, light and dark, the 

 light form being abundant in from four inches to 22 feet of 

 water. " It is, however, dominant in shore, in weedy patches 

 (Potanwgeton and C crate phyllum) and on CAara-covered bot- 

 toms. The dark variety occupies the same region but is 

 dominant upon sand and gravel bottoms in from three and a 

 half to 22 feet of water. The intergrading forms cover the 

 same territory as the straw-colored and dark varieties but 

 can not be said to be dominant anywhere." These authors 

 conclude (p. 178) that " wave action and the muskrat deter- 

 mine the limit of the distribution shoreward and that the 

 character of the bottom is the principal factor determining the 

 outer boundary of the zone." Some very ingenious experi- 

 ments are recorded testing the ability of various mussels to 

 withstand changes of environment. It will be remembered that 

 mussels were found in Oneida Lake at all depths examined 

 (one to 18 feet), occurring very abundantly in soft black mud 

 in water 8 to 18 feet deep. 



In rivers and streams the mussels are found on a variety of 

 bottoms and at varying depths. In the Illinois River at Beards- 

 town, they occur in sand and mud in water from 10 to 12 feet 

 deep. Above the LaGrange locks they are found on a mud 

 bottom in 8 to 12 feet of water (Danglade, '14, p. 20). In the 

 Cumberland River, below Livingston, the mussels occur on a 

 rocky bottom (in clay between rocks) in a maximum depth of 



