Sterki: North American Sph/eriid.^. 455 



Very variable. 



Habitat. — ^East of the Mississippi River; New England and New 

 York to Illinois (the more typical form), especially in spring brooks. 

 Fossil. — New Jersey, Michigan. 



45. Pisidium noveboracense expansum Sterki. 



Pisidium noveboracense var. expansum Sterki, Nautilus, XIX, 1906, p. 118. 

 Habitat. — Michigan. 



46. Pisidium noveboracense quadrulum Sterki. 



Pisidium noveboracense var. quadrulum Sterki, Nautilus, XIX, 1906, p. 119. 

 Habitat. — Ohio, spring marshes. 



47. Pisidium noveboracense lineatum Sterki. 

 Pisidium noveboracense var. lineatum Sterki, I. c, p. 119. 



Habitat. — Michigan lakes. 



48. Pisidium noveboracense fraternum Sterki. 



Pisidium noveboracense var. fraternum Sterki, I. c, p. 120. 

 Habitat. — Ohio, Illinois. 



49. Pisidium noveboracense alabamense Sterki. 

 Pisidium noveboracense var. alabamense Sterki, I. c, p. 120. 



Habitat. — Alabama, Mississippi. 



50. Pisidium elevatum Sterki. 



Pisidium noveboracense var. elevatum. Sterki, /. c, p. 1x9. 

 Appears to be a distinct species. 

 Habitat. — Ohio, Illinois, Ontario. 



51. Pisidium regulare Prime. 



Pisidiufn regulare Prime, Boston Journ., VI, 1852, p. 363, PI. XII, figs. 11, 12; 

 Mon. Corb., 1865, p. 68, as synonym of P. abditutn. 



Habitat. — Michigan, Ontario. 

 Fossil. — Michigan. 



52. Pisidium regulare (?) danieisi Sterki. 



Pisidium danieisi Sterki, Nautilus, XVII, 1903, p. 42. 



Somewhat larger, beaks broader, surface striae coarser, color more 

 yellowish. 



Habitat. — Michigan, Indiana. 



