Occasional Papers of the Museum of Zoology 27 



Habitat 41. Hardwoods of Calumet Trough. The higher 

 moraines throughout the Calumet Trough have a more clayey 

 soil than the outwash plains and form conspicuous hardwood 

 ridges. The fires had not affected this habitat as much as they 

 had Habitat 38, although ground fires had killed the under- 

 brush and burned through the upper humus over considerable 

 areas, especially at the edges. Except for this, the woods are 

 practically in their primitive condition and form magnificent 

 and extensive forests. They consist of sugar maples (Acer 

 sarcharum), yellow birches (Betula lutea), basswoods {Tilia 

 americana ) , hemlocks {Tsuga canadensis), balsam firs (Abies 

 balsamea), blue beeches (Carpinus caroliniana) , ironwoods 

 (Ostrya virginiana) and elms (Ulmus amcricamts), which 

 were abundant in the order named. The hemlocks and balsam 

 firs were most commonly near the edges of the woods, where 

 some arbor vitae (Thuja occidentalis) strayed in from adja- 

 cent damper habitats. The underbrush consisted mainly of 

 small maples and the whole forest was carpeted with a thick 

 layer of leaves and humus in the unburnt places. In the burnt 

 places the larger logs were usually but little affected and still 

 contained large numbers of living shells. 



Most of the snails were obtained from just under the outer 

 bark among the decaying inner bark and the effluvia of beetle 

 larvae, myriapods, etc. The greatest number were found in 

 quite soft and punky logs, whose bark was easily peeled away. 

 Maple logs contained most of them ; the hemlocks, especially, 

 have a dry and white or slimy mould growing under the bark, 

 which appeared to be coincident with conditions unfavorable 

 to molluscan life. 



Of the larger species, Pallifcra dorsalis was only obtained 

 from one locality, an especially rich portion of the unburnt 



