466 Annals of the Carnegie Museum. 



104. Pisidium ventricosum Prime. 



Pisidiiim ventricosum Prime, Boston Proc, 1851, p. 87; Mon. Corb., 1865, p. 72. 

 Habitat. — New England (common); Kew York, Michigan (rare). 

 Fossil.- — Maine, Michigan. 



105. Pisidium vesiculate Sterki. 



Pisidium vesiculare Sterki, Nautilus, X, 1896, p. 21. 

 Habitat. — Region of the Great Lakes. 

 Fossil.- — Michigan. 



106. Pisidium vesiculare striatellum var. nov. 



Beaks broader, surface with a silky gloss from the sharper stride, 

 shell more translucent, nearly colorless. 



Habitat. — -Collected by Mr. L. E. Daniels, 1903, in Lake Maxin- 

 kuckee, Indiana, in waters from fourteen to eighteen feet deep (Carn. 

 Mus. No. 4702). 



107. Pisidium medianum Sterki. 



Pisidium medianum Sterki, Nautilus, XIII, 1899, p. 10. 



Habitat. — Region of the Great Lakes, common, especially in Michi- 

 gan, which seems to be the center of distribution, Mohawk, N. Y., 

 Ohio, also in Ohio River drainage. 



Fossil. — Ontario, Michigan, Ohio, Illinois. 



108. Pisidium medianum clarum var. nov. 



Large for the species, somewhat elongate, shell translucent to 

 transparent, amber-colored. 



Flabitat. — Clear Lake, Steuben County, Indiana, collected by Mr. 

 L. E. Daniels, July 7, 1904 (Carnegie Museum, No. 4878); similar, 

 but somewhat smaller specimens were collected by Mr. Bryant Walker 

 in Hillsdale County, Michigan, in 1900. 



109. Pisidium medianum minutum Sterki. 



Pisidium medianum var. minutum Sterki, Nautilus, XIII, 1899, p. 11. 

 Habitat. — Maine, Massachusetts, New York. 

 Fossil.- — Maine. 



no. Pisidium costatum Sterki. 



Pisidium costatum Sterki, Nautilus, XVII, 1903, p. 22. 



Fossil. — Maine, Michigan. (Probably also recent.) 



