Sterki: North American Sph.-eriid^. 451 



24. Pisidium punctatum Sterki. 



Pisidium punctatum Sterki, Nautilus, VIII, 1895, p. 99, PI. II, figs. 7 12, 14. 

 Habitat. — Maine to Virginia and Minnesota. 

 Fossil. — Illinois (loess). 



25. Pisidium punctatum armatum Sterki. 



Pisidium punctatum var. armatum Sterki, Nautilus, XIX, 1905, p. 84. 

 Habitat. — Ohio. 



26. Pisidium punctatum simplex Sterki. 



Pisidium punctatum var. simplex Sterki, Nautilus, XIX, 1905, p. 84. 



Habitat. — New England to Ohio, Indiana, Illinois, Wisconsin, 

 Michigan, Missouri; Cf. No. 23. 



27. Pisidium limatulum Sterki. 



Pisidium limatulum Sterki, Nautilus, XVIII, 1905, p. 108. 

 Habitat. — Alabama to Texas; northeastern Ohio. 



28. Pisidium handwerki Sterki. 



Pisidium handwerki Sterki, Nautilus, XIII, 1899, p. 90. 

 Habitat. — Illinois, Michigan. 



29. Pisidium aequilaterale Prime. 



Pisidium cequilaterale Prime, Boston Journ., VI, 1852, p. 366, PL XII, figs. 23-25; 

 Mon. Corb , 1865, p. 63. 



Habitat. — Maine to New York and Virginia, Ontario (Ottawa 

 River); reported from Michigan and northward and westward, but 

 I have seen no specimens from those regions. 



Fossil.— New Jersey. 



30. Pisidium fraudulentum Sterki. 



Pisidium fraudulentum Sterki, Nautilus, XXVI, 1912, p. 95. 



Somewhat variable. 



Habitat. — ^Eastern Virginia, Kentucky, Illinois, Iowa, Missouri, 

 Mississippi. 



31. Pisidium fraudulentum peraltum Sterki. 

 Pisidium peraltum Sterki, Nautilus, XIV, 1900, p. 5 (partim). 



Smaller than P. fraudulentum, less oblique; the beaks are fuller and 



