BIOLOGY OF PHYSA 35 



moss. Another specimen of L. palustris was found upon some dry 

 Hypnum with its aperture up and a mucous epiphragm over it. 

 No signs of an inwash from the surrounding clay and sand hills 

 were seen and no evidence was seen of burrowing on the part 

 of the snails. 



Swamp B.^ This swamp is a small, open area situated in a 

 growth of poplar trees. Some willow trees skirt its borders 

 and fill the substratum of peat with small rootlets. Rotting 

 logs, brush and willow leaves are found on the swamp bed which 

 has a growth of such mesophytic plants as the dandelion and 

 thistle. No water plants were seen except some algae. A thorough 

 search in this debris and peat for evidence of the habit of burrow- 

 ing among snails revealed nothing but a number of living Sphae- 

 rium buried in places to the depth of three inches. Two speci- 

 mens of Lymnaea palustris were found lying aperture down on 

 the surface amid loose peat and dead shells. Several living 

 Physa elliptica and Lymnaea palustris were found, aperture 

 down, in a thin wash of clay on the border of the swamp. The 

 ground around this swamp is grass-grow^n and the hills gently 

 sloping; this perhaps accounts for the small amount of erosion 

 found. 



Swamp B.^ This swamp is situated at the foot of low cultivated 

 hills of clay and sand, some of which are in pasture, others in 

 grain, and still others are freshly ploughed. The swamp is only 

 partly denuded of its trees of white cedar and black ash, some 

 of w^hich are growing, while others have been felled and allowed 

 to decay. A dense, thick border of willows skirts the swamp, 

 causing it to be more shaded in these parts. The sw-amp has 

 a dense growi:h of Hypnum which covers the logs and sub- 

 stratum. 



In this swamp, of fully fifteen acres, there w^as found very 

 little evidence of living molluscan life although there were 

 many dead shells lying about upon the peat and moss. One 

 or two living specimens of Lymnaea palustris were found on 

 the border of the swamp in the damper places, and one or two 

 were found sealed in the clay which had washed over the peat, 

 but no other living mollusks were found except a few bivalves 

 in the peat on the border of the swamp. Absolutely no signs of 

 life were found in it, on or beneath the heavy blanket of Hypnum. 

 Even the Sphaerium buried beneath the heavy growth of moss, 



