296 MICHIGAN SURVEY, 1908. 



pools with gravel bottom in the outlet from Siskowit Lake and at tlie 

 margin of Sumner Lake. 



62a.* var. hrevins Sterki. 



Range: "Michigan; Minnesota aud Keewatin." (Sterki.) 



Michigan : Upper Peninsula and northern part of the Lower Pen 

 insula. 



Isle Royale: III, 3, Bulrush Zone, Rock Harbor, Nos. 160, 164. All 

 the examples both of the typical form and the variety are "small ajad 

 mostly immature." 



With the typical form in the mud bottom in 3-5 feet of water at the 

 head of Rock Harbor; 



63.* Pisidium affine Sterki. 



Range: "Great Lake Region, Michigan to New York; Minnesota, 

 Illinois and Ohioi (Ohio River Drainage)." (Sterki). 



Michigan : Generally distributed. 



Isle Royale: III, 5, Sumner Lake, Nos. 77 A, 79 A. A few ex- 

 amples, "quite small," from the margin and Sedge Zone. 



64.* Pisidium sargenti Sterki? 



Range: "Northern United States, New York to Minnesota." (Sterki). 



Michigau: Generally distributed in Lower Peninsula; Isle Royale. 



Isle Royale: III, 5, Sumner Lake, No. 176. Two specimens only, 

 which "may be Pisidiwm sargenti. One example is large, especially in 

 contrast with the small forms of the other species. In the smaller 

 specimen the hinge is partly reversed." 



65.* Pisidium scutellatum Sterki. 



Range: Northern United States, Michigan to Washington and 

 northward. 



Michigan: Generally distributed. 



Isle Royale: III, 2, Small Island in Rock Harbor, No. 89; III, 3, 

 Bulrush Zone, Rock Harbor, Nos. 159, 160, 163, 164; "Small, north- 

 ern variety. The most common species and somewhat variable." 



In the mud and silt bottom in 10 inches to 5 feet of water ait the 

 upper end of Rock Harbor (Nos. 159, 160, 163). 



66.* Pisidium, roperi Sterki. 



Range: Northern United States, Maine to Minnesota. 



Michigan: Generally distributed. 



Isle Royale: III, 5, Sumner Lake, No. 78; IV, 8, Trail to Green- 

 stone Range, No. 128. "Small, but good and characteristic." 



67.* Pisidium ventricosum Prime. 



Range: Northern United States, Maine to Michigan and northward. 



Michigan : Western part of the State, Kent County to Charlevoix 

 County; Marquette County; Isle Royale. 



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

 Island in Rock Harbor, No. 89; III, 3, Bulnish Zone at Rock Harbor, 

 Nos. 163, 164. 



In 10 inches of water in the Potamogeton Zone at the mouth of a 

 creek at the upper end of Rock Harbor (No. 163) and at the margin 

 and in the sedge of Sumner Lake. 



68.* Pisidium subrotundum Sterki. 



Range: "New England; Anticosti Island to Michigan." (Sterki). 



Michigan : Kent, Marquette and Ontonagon counties and Isle Royale. 



