434 Annals of the Carnegie Museum. 



10. Sphserium stamineum forbesi Baker. 



Nautilus, XXII, 1906, p. 21. 



Habitat. — Illinois, Michigan, Ohio River at Cincinnati, Maryland, 

 and Virginia. 



11. Sphaerium stamineum wisconsinense var. nov. 



Smaller than average stamineum, not so high, less inflated, superior 

 margin less curved; surface striae moderately coarse to obsolete; color 

 light corneous to grayish; shell and hinge slighter. 



Habitat. — Wisconsin, Michigan. 



Fossil. — Illinois, post-glacial deposits of Chicago. 



12. Sphaerium emarginatum (Prime). 



Cyclas emarginala Prime, Boston Proc, IV, 1851, p. 156. 

 Sphmium emarginatum Prime, Man. Corb., 1865, p. 43. 



Habitat. — Maine to Lake Superior, Winnipeg, Keewatin. 



13. Sphaerium torsum sp. nov. 



Mussel inequipartite, oblique, well-inflated, posterior part higher, 

 and much more voluminous than the anterior; dorso-ventral axis 

 curved and oblique; beaks strongly inclined forward, large, prominent, 

 rounded, not, or slightly, mamillar; superior margin curved, not, or 

 barely, bounded by angles; scutum and scutellum well marked; 

 anterior and posterior ends rounded, inferior margin moderately 

 curved; surface with fine, slight, irregular or subregular concentric 

 striae and a few lines of growth, shining; yellow, straw-colored in 

 younger specimens; shell moderately strong; hinge long for the shape 

 and size of the mussel, almost regularly curved, rather slight; cardinal 

 teeth small, the left posterior tooth vestigial in some specimens; 

 laminae rather slight, at almost a right angle to each other; ligament 

 covered, resilium moderately strong. Soft parts not examined. 

 Long. II mm.; alt. 9 mm.; diam. 7 mm. (100 : 83 : 64). 



S. torsum appears to range near emarginatum of the same region, 

 but is more oblique, of more rounded outlines, more evenly inflated. 

 The beaks are less elevated, less mamillar, and more inclined forward, 

 and the hinge is much slighter. 



Habitat. — Quebec, Ontario, along the Ottawa River near Hull and 

 Ottawa, collected by Justice F. R. Latchford, 191 1 and 1912. Types 

 in the collection of Mr. Latchford, and No. 6956 for full-grown, and 

 7286 for young and adolescent specimens. It occurs also in Wisconsin. 



