28 University of Michigan 



hardwoods along the road to Foster City. Of the smaller 

 forms, Zonitoides arhorea was as abundant as all of the rest 

 put together; Strobilops virgo made up about half of the 

 remainder; and Ga^trocopta contrada and Pyramidula cronk- 

 hitei catskillensis together formed the major portion of the 

 remaining fourth, except in one locality where the last two and 

 Euconnlus chersinns polygratus were about equally numerous. 



LACUSTRINE PEAT-BOG ( TABLE v) 



Habitat 42. Cedar-tamarack Bog. Northeast of Brown 

 Lake a depression in the outwash plain contained a small bog 

 which was grown up with arbor vitae, spruce (Picea cana- 

 densis), tamarack {Larix laricina), with here and there a few 

 balsam firs. A thick undergrowth, especially around the edges, 

 consisted of young trees mixed with tag-alders {Alnus incana), 

 willows and dogwoods. The entire bog was carpeted with 

 sphagnum and dwarf cranberry {Vaccinium oxycoccus) and 

 considerable growth of Labrador tea {Ledum groenlandicuni) 

 was present. The shells were found under the bark of quite 

 freshly cut cedar stumps. 



STREAM ALEUVIAE (TABEE v) 



Swamps 



Habitat 4J. Arbor Vitae Swamp near Sand Portage. A num- 

 ber of shells were collected in a swampy thicket around the 

 mouth of a small creek near Sand Portage. This thicket con- 

 sisted mainly of arbor vitae, tag-alders, white birches, balsam 

 firs, poplars and ashes. The shells were found among the 

 leaves and the humus. 



Habitat 44. Ash-cedar Swamp. This is the same swamp 

 described in Habitat 15. The land shells were collected in the 

 humus around the bases of the trees. 



