177 



To sum up: In the liMsket in twenty-tive feet, lowered on dai'k ni;irl. 

 in nineteen days ti\e were found dead and four niissiiiy; in the basket 

 in tliirty-tive feet, h)wered near Sandy Point on a sandy gray marl bottom, 

 in fifteen days one was dead, all showed .sill>^ partly tilled with sediment; 

 in tlie Itasket in ei.uhty-tive feet, lowered on pure dai'lc marl, in nine 

 days two were found dead and tlie uills of all liut A. edentiila badly 

 ehoked with sediment. T'. fal)alis. U. .i;lans and V. snlirostratus were not 

 inchidt'd in this experiment lieeause the tirst two woidd have slipped out 

 throu.uh the meshes and the third eould not be obtained at the time. 

 HoAA'ever. it seems reasonable to supi)ose that they would have proven 

 not unlike the others. It seems, therefore, that those foi'nis possessing 

 light weight in prop(»rtion to surface e.xposed and close-titting valves 

 are best able to i-esist the soft marl and the overlying sediment. 



A. grandis and edentula. having light and close-titting valves, are 

 fotuid accordingly on the outer edge of the sandy marl liank; the edentula, 

 being better fitted to withstand the bottom ooiulitions, is found out 

 in the edge of the dark marl. V. glans and fabalis. owing to lightness and 

 close-fitting valves, ocetipy alxmt the same sittiation. the fabalis having 

 much the lighter shell, lieiug found out as far or farther than the 

 edentula. They are also found inshore, where not subjected to wave 

 action. U. suln'osti'atus. liaving nu'diuni weight valves, which are also 

 close-fitting, is confined to the gravel and sand banks, weed patches and 

 chara-covered beds. U. ruVtiginosis, having very heavy and rather loose- 

 fitting valves, is eonlined to clear sand and gravel banks. The dark 

 form of luteolus. having extremely heavy and rather loose-fitting valves, 

 is confined to hard sand and gravel banks. The straw-colored form by 

 its medium weight and tight-fitting valves is alile to live on sand, gravel, 

 in mud patches and on chara-covered bottoms. Owing to the fact that so 

 few specimens of M. marginata were found we were unable to draw any 

 conclusions as to its ecology. 



The muskrat is the principal enemy of the mussels: around his 

 house many mussel shells are found, but no live mussels. Shells of 

 all the species in the lake except the smaller ones are found, the Ano- 

 donta shells being in much greater evidence than is proportionate to 

 their total number. They do not appear so on first examination, for 

 they are Inoken up l)y the animal and worn by the waves. The con- 

 ditions on the sand lianks ))eyond reach of wave action are very favor- 



12— A. or SciE.vcF.. '03. , 



