ECOLOGY OP ISLE ROYALS. 297 



Isle Royale: I, 6, Sphagnum-Spruce Bog, No. 116; IV, 8, Trail to 

 Greenstone Range, No. 128; III, 3, Bulrush Zone at western end of 

 Rock Harbor, Nos. 159, 160; I, 4, Tamarack and Arbor Vitse Swamp, 

 Nos. 181, 182 ; V, 5, Tamarack Swamp, No. 237 ; V, 9, Outlet of Siskowit 

 Lake, No. 238. A "form" of this species "common and somewhat vari- 

 able." 



Among dead leaves and sedges at the bottom of shallow pools in a 

 tamarack swamp (No. 116). In silt and debris on the bottom in 4-5 

 feet of water (Nos. 15.9, 160) ; small sphagnum-lined pools, seldom 

 exceeding six inches in depth in dense shade (Nos. 181, 182) ; among 

 sphagnum and Utricularia in small streams and pools, mostly in the 

 sun (No. 237) ; in shaded, shallow pools with gravelly bottom (No. 

 238). 



69.* Pisidiwn rotundatiim, Prime. 



Range : Northern United States, Maine to Minnesota and . north- 

 ward. 



Michigan : Generally distributed. 



Isle Royale: I, 6, Sphagnum-spruce Bog, No. 116; III, 3, Bulrush 

 Zone, Rock Harbor No. 160; V, 5^ Taiuarack Swamp, No. 237; "Pew 

 and probably none mature." 



Among dead leaves and sedges at the bottom of shallow pools, in 

 shade (No. 116) ; among sphagnum and Utricularia in small, shallow 

 streams and pools, mostly in the sun (No. 237.) 



70.* Pisidimn splendidulum Sterki. 



Range: Northern United States, Maine to Michigan. 



Michigan : Generally distributed. 



Isle Royale: III, 5, Sumner Lake, Nos. 77 A, 79 A, 176. At margin 

 and in the Sedge Zone. 



71.* Pisidium paupercuhim Sterki. 



Range: Northern United States, Maine to Minnesota. 



Michigan: Generally distributed. 



Isle Royale: III, 3, Bulrush Zone at western end of Rock Harbor, 

 No. 164. A few specimens of a small form. 



72.* Pisidium medianum Sterki. 



Range: Northern United States, Maine to Wisconsin. 



Michigan : Generally distributed. 



Isle Royale: III, 5, Sumner Lake, Nos. 77 A, 78 A, 79 A; III, 2, 

 Small Island in Rock Harbor, No. 89 ; III, 3, Bulrush Zone at western 

 end of Rock Harbor, Nos. 160, 164; V, 9, Outlet of Siskowit Lake, 

 No. 238. 



Near the mouth of a small creek, on a silt and mud bottom at a 

 depth of 5 feet (No. 160) ; In shallow, shaded pools with gravelly 

 bottom (No. 238). 



73.* Pisidium punctatum simplex Sterki. 



Range: "Michigan, Wisconsin and Illinois." (Sterki.) 



Michigan: Carp Lake, Emmet Co. and Isle Royale. 



Isle Royale: III, 3, Bulrush Zone at Western end of Rock Harbor, 

 No. 160. 



74.* Pisidium milium Held. 



Range: Europe; Maine and Michigan. 



Michigan: Generally distributed. 



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