i6 University of Michigan 



River material, represent a distinct species, dcclivc, of wide 

 distribution, and rather variable." (Sterki.) 



Sphccriiiiu sitlcatiiiu (Lam.). Sheyenne River. 



Sphserium sp. Sheyenne River. "^lay be a form of staiii- 

 incitm:' (Sterki.) 



Musciiliiiiii jayciisc ( Prime j. Sheyenne River. 



Miisculiiiin trans: ersiiiii (Say). Sheyenne River. 



Musculium sp. ^lauvaise Coulee. "Apparently a species 

 distinct from all described, at any rate markedly different, 

 from jaxciisc, truncatnin, forms, and ryckholti Xormand, the 

 only ones which it somewhat resembles. Alay yet be a form 

 (or forms) of truncation Lins." (Sterki.) 



Pisidium apiculatiini Sterki (MS). Upsilon Lake. Found 

 in gravel bottom a few feet from shore, where the water was 

 from one to two feet deep. Xone were obtained from muddy 

 or mucky bottom. 



Pisidiuni coniprcssuni Prime. Sheyenne River, Upsilon 

 Lake. Gravel Lake. "Exceptionally small form'" from Upsi- 

 lon Lake. 



Pisidiuni contortuni Prime. Gravel Lake. 



Pisidiuni paupcrculuni Sterki. Gravel Lake. 



Pisidiuni tcnuissiniuni Sterki. Court Lake, Fort Totten 

 Lake. 



Pisidiuni lariahilc Prime. Gravel Lake. 



Pisidiuni ivriabile bre: iits Sterki. Upsilon Lake. 



Pisidiuni vcsiculare Sterki. Court Lake. 



Pisidium sp. Gravel Lake. "Apparently form of tcnuissi- 

 niuni. very much like a form ('calcareuni' ) so far found fos- 

 sil (common) in marls of Maine, Michigan, and Illinois.'' 

 (Sterki.) 



