ORTMANN: monograph of the naiades of PENNSYLVANIA. 281 



gravelly bottom and strong, steady currents. In smaller streams it is also mostly 

 in very strong currents and in heavy gravel on riffles. It buries very deeply. 

 In Lake Erie it is found in the fine sand and gravel of Presque Isle Bay, in pro- 

 tected locations (among rushes) as well as on open, surf-beaten shores. It is also 

 in some of the beach-pools with quiet water and sandy-muddy bottoms. 



General distribution : Type locality, Lake Erie (Lamarck). 



The metropolis of E. recta is in the large rivers of the central basin. From 

 western Pennsylvania, it spreads all through the Ohio-drainage in Ohio (Sterki, 

 1907a), Indiana (Call, 1896a, 1900), in West Virginia, and eastern Kentucky. 

 From the rest of Kentucky records are lacking, but it is in the Cumberland (Mar- 

 shall, 1895; Wilson & Clark, 1914), and in the Tennessee, where it ascends in the 

 Clinch River to Virginia. It is conamon in the Mississippi-drainage in Illinois 

 (Baker, 1906), Iowa (Pratt, 1876; Witter, 1878; Call, 1895; Marshall, 1895; 

 Geiser, 1910), and northward to Wisconsin (Conrad, 1836; Cooper, 1855; Lapham, 

 1860), and Minnesota (Cooper, 1855; Grant, 1886; Holzinger, 1888). 



In the Missouri-drainage, it is found in Missouri (Utterback, 1916), in north- 

 eastern Kansas (Scammon, 1906), and southeastern Nebraska (Tryon, 1868; Call, 

 1895). Southward it becomes less abundant, but is known from the southern 

 drainage in Kansas (Scammon), Arkansas (Call, 1895; Marshall, 1895; Wheeler, 

 1918), and Oklahoma. Its presence in Texas is doubtful. 



In addition this species has crossed over into other drainages in the north 

 as well as in the south. From northern Indiana and Ohio it has reached the 

 lake-drainage in IVIichigan (Walker, 1898) and Lake Erie (Walker, 1913), and has 

 spread down the St. Lawrence far into eastern Canada, Ottawa, Quebec, Montreal 

 (See BeU, 1859; Whiteaves, 1863; CaU, 1885; Marshall, 1895) and has entered 

 some of the tributaries of the St. LawTence in western New York (Marshall, 1895). 

 In Ontario it goes northwest at least to the region of Georgian Bay, Severn River 

 (See Carnegie Museum). Fm-ther in Minnesota it has crossed over into the 

 drainage of the Red River of the North, Wilkin County (Grant, 1886), and has 

 reached North Dakota, at Pembma (Call, 1885) and Roseau River (Dawson, 1875), 

 Winnipeg (Christy, 1855; and Hanham, 1899) Canada. 



Finally it is found in the south in the Alabama-drainage in Alabama and 

 Georgia (Conrad, 1836; Lewis, 1877; Call, 1885, 1895). 



As has been said, it prefers larger rivers, and within the immense area indi- 

 cated above, it may be missing in many of the smaller, and even medium-sized 

 streams. Baker (1898a) records it from lakes and large rivers, on muddy bottoms, 

 while Scammon (1906) says that it is found under a variety of conditions. 



