130 LAND AND FRESH WATER MOLLUSKS 



perhaps the upper St. Lawrence localities may owe its presence to 

 capture of part of the Mississippi drainage, owing to changes of level, 

 elsewhere referred to. 



Anodonta kennicotti Lea. 



Anoilonta kennicotti Lea, Proc. Acad. Nat. Sci. Phila., v, p. 56, 1861 ; Jour- 

 nal, n. s., V, p. 214, pi. .\xxiii, fig. 283, 1862. 



Anodonta siinpsoniana Lea, op. cit., p. 56, 1861 ; p. 212, pi. XXXII, fig. 

 281, 1862. 



Anodonta dallasiana Lea, Proc. Acad. Nat. Sci. Phila., vii, p. 190, 1863 ; 

 Journal, vi, p. 29, pi. xi, fig. 28, 1866. 



Range, — Upper and middle St. Lawrence system. Mackenzie 

 drainage to Great Slave Lake. 



Lake of the Woods ; Manitoba Lake ; Lake Winnipeg ! Grand 

 Rapids of the Saskatchewan ! Ekwan River, Keewatin ; Fort Simp- 

 son, Mackenzie River ! Fort Erie and Fort Rae ! Great Slave Lake ; 

 Buffalo Lake, Methy Portage, Saskatchewan. 



This is the most characteristic Naiad of the central Boreal region 

 and reaches perhaps farther north (Lat. 63°) than any other species in 

 American waters. 



Anodonta pepiniana Lea. 



Anodonta pepiniatta\jE.^., Trans. Am. Phil. See, vi, p. 96, pi. xvi, fig. 51, 1838. 



Range. — Upper and middle St. Lawrence drainage, Saskatche- 

 wan basin. 



Lake Winnipeg ! Manitoba. Attawapiskat River, eastern Keewatin. 



Genus Gonidea Conrad. 



Gonidea angulata Lea. 



Anodonta angulata Lea, Trans. Am. Phil. Soc, vi, p. 97, pi. xvi, fig. 52, 1838. 

 Anodon fcminalis Gould, Proc. Boston Soc. N. Hist., iii, p. 293, 1850 ; Moll. 



U. S. Expl. Exp., p. 436, pi. xxxviii, figs. 547, a-b, 1852. 

 Anodonta randal/i Tv.a?,k, Proc. Acad. Nat. Sciences Calif., I, p. 28, 1855. 

 Anodon iiang-u/ata Sowekby, Conch. Icon., xvii, pi. xxiii, figs. 8, a-i, 1869. 



Range. — Central California, north to British Columbia and east- 

 ward to Idaho. 



Columbia River near Fort Colville ! 



This singular shell hardly more than crosses the boundary, so far as 

 reported. According to Stearns and Hemphill this species buries itself 

 obliquely in the rather hard bed of rapid streams, so that the flattened 

 posterior portion lies horizontally even with the bottom, and offers no 

 resistance to the current. Whether the flattening and consequent angu- 

 lation of the valves is a modification due to the burrowing habit and 

 the influence of its environment, or not, cannot yet be positively stated. 



