Sterki: North American Sph.criid.e. 457 



Habitat. — Ohio (Carn. Mus., No. 3407); Illinois (Carn. Mus., No. 

 984); Michigan (Carn. Mus., No. 2655). 



61. Pisidium succineum Sterki. 



Pisidium succineum Sterki, Nautilus, XX, 1907, p. 99. 



Habitat. — Massachusetts, New York, Pennsylvania to Virginia, 

 Ontario, Ohio, Indiana, Michigan. 



62. Pisidium scutellatum Sterki. 



Pisidium scutellatum Sterki, Naiililui, X, 1896, p. 66. 



Very variable, and there are several well-marked varieties. 



Habitat. — Lake Champlain, Vermont; region of Great Lakes and 

 as far west as Montana; Yukon Territory. 



63. Pisidium walkeri Sterki. 



Pisidium walkeri Sterki, Nautilus, IX, 1895, p. 75. 



Habitat. — Maine to Virginia and Ontario, Missouri, South Dakota. 

 Fossil. — Illinois (marl and loess). 



64. Pisidium overi Sterki. 



Pisidium overi Sterki, Nautilus, XXVI, 1913, p. 136. 

 Habitat. — South Dakota, Iowa, Minnesota. 



65. Pisidium mainense Sterki. 



Pisidium walkeri var. maineyise Sterki, Nautilus, XII, 1898, p. 79. 

 This is a distinct species. 



Habitat. — Maine, Massachusetts, Ontario, Ohio, Michigan, Illinois. 

 Fossil. — Maine, Ontario, Ohio, Michigan, Illinois. 



66. Pisidium cuneiforme Sterki. 



Pisidium ciineifor77ie Sterki, Nautilus, XVII, 1903, p. 81. 

 May range near P. conipressum. 

 Habitat. — Lake Michigan, obtained by dredging. 



67. Pisidium superius Sterki. 



Pisidium superius Sterki, Nautilus, XX, 1907, p. 98. 



Habitat. — Northern Michigan, Lake Nipissing, Ontario. 



68. Pisidium steenbuchi (Moller). 



Cyclas steenbuchii Moller, Index Moll. Granlandice, 1842, p. 20. 

 Pisidum steenbuchii B. B. Woodward, British Pisidia, 1913, p. 107, figs. 



Habitat. — Palearctic and Nearctic Regions; Greenland; Labrador, 

 Ungava. 



