Sterki: North American Sph^riid^. 449 



Habitat. — Palearctic and Nearctic regions. Lake Champlain. 

 "Lake Superior to Lake Winnipeg (Richardson)" cited from Dall, 

 Alaska, Mollusca, p. 145. 



18. Pisidium cruciatum Sterki. 



Pisidium cruciatum Sterki, Nautilus, VIII, 1895, p. 97, PI. II, figs. 1-6, 13. 



One of the most remarkable of all Pisidia, especially on account 

 of its hinge and the shape of the umbonal ridges, combined with its 

 small size (2 mm, long). 



Habitat. — Ohio, Michigan, Illinois, Missouri, Arkansas, Alabama. 



Fossil. — Illinois (lower loess). 



19. Pisidium kirklandi Sterki. 



Pisidium kirklandi Sterki, Nautilus, XIII, 1899, p. 11. 

 ' Habitat. — Ohio, Michigan, Illinois, Alabama. 



20. Pisidium fallax Sterki. 



Pisidium fallax Sterki, Nautilus, X, 1896, p. 20. 



Habitat.— New Jersey to South Dakota, Ohio River, Lake Erie. 



Fossil. — Michigan, New York (Goat Island, Niagara), Ohio, 

 Illinois. 



21. Pisidium fallax mite Sterki. 



Pisidium fallax var. mite Sterki, Nautilus, XIX, 1905, p. 84. 

 Habitat.^Ohio, Michigan. 



22. Pisidium fallax septentrionale Sterki. 



Pisidium fallax var. sepentrionale Sterki, Nautilus, XII, 1898, p. 78. 

 Pisidium fallax var errans Sterki, Nautilus, XIX, 1905, p. 84. 



(It is the opinion of Dr. Bryant Walker that the arrangement should 

 be as here given. Prime's P. septentrionale not having been described.) 

 Markedly different from P. fallax. 

 Habitat. — Northern Maine, Michigan, Minnesota, Iowa, Keewatin. 



23. Pisidium hinkleyi sp. no v. 



Mussel small, subtriangular, very inequipartite, oblique, moder- 

 ately inflated; superior margin strongly curved, posterior rounded, 

 forming one continuous curve with the inferior from the beaks to the 

 rounded-angular anterior end situated well below the longitudinal 

 median line; supero-anterior slope well remote from the beaks, slightly 

 marked and somewhat curved, short, steep; beaks near the posterior 



