17C 



ficient to smother it. That there is an overlying; sediment is shown 

 by the following- experiment: "NVe iiumped water from twelve and six 

 inches aliove tlie sandy and gravelly bottom in seven, ten, fifteen, 

 twenty-five feet of water: the specimens revealed no sediment that 

 would not settle on standing. Specimens were taken in thirty and 

 thirty-six feet of water over a marl bottom and the twelve-iueh samples- 

 yielded a small amount of such sediment, while the six-inch samples 

 showed a decided amount. That matter in suspension is fatal to the 

 mussel is shown liy the fact that we found in the west side and south 

 end of the lake Avhat were evidently once thriving mussel beds, bm-ied 

 under a thin layer of coarse marl, which had been stirred up by the 

 action of the steam dredge two years before. These mussels were 

 found in the normal position undisturbed in any way. That the mussels 

 were alive five years ago is shown by Dr. Moenkhaus' statement that 

 he and his classes collected an ahundance for study in those same regions 

 at that time. 



In order to lest the ability of the mussel to stand these l)()ttom 

 conditions we made three wire clam baskets, lowered one in twenty- 

 five feet of walei-. anoth(>r in thirty-five feet, another in eighty-five 

 feet. We got the following results: 



August .">, a basket containing thiiti'cn I', luteolus and one A. grandis 

 was placed in L'.") feet of w.iier du a dark marl bottom. On the loth 

 two examples (if T'. lutenlus were dead: on the l."»th one U. luteolus was 

 dead: on tlie ITtli two V. luteohis \\erc dead and four were missing. 



August '.1. .-I basket cnntaining five U. luteolus of the light variety 

 and one of tlie dark, .iiid diie .\. (deiitula was lowered in .".5 feet of water 

 on a sandy gray marl liottoni. On the l.lth, one A. grandis and one U. 

 rubiginosus were added. On the I'tith one U. luteolus of dark \ariety 

 was dead: on the 24tli five U. luteolus and one U. rubiginosus were found 

 -to have the gills badly choked witli sidiment, while the anodontas were 

 missing. 



August iri, a basket containing seven U. luteolus of light and oiu^ of 

 dark variety, two A. edentula. and one A, grandis was lowered in So 

 feet on a pure dark marl lioitom. On the 21st one U. luteolus of dark 

 variety was dead: on the 24th seven 1'. luteolus and one A. grandis 

 showed gills liadly choked with sediment, while the two edentula were iu 

 better condition, showing very few patches of marl in gills. 



