306 MEMOIRS OF THE CARNEGIE MUSEUM. 



Black River (H. E. Wheeler), and Spring River (A. A. Hinkley), Black Rock, Lawrence Co., Arkansas. 

 Illinois River, Tahlequah, Cherokee Co., Oklahoma (F. B. Isely). 

 Fourteen Mile Creek, Fort Gibson, Muskogee Co., Oklahoma (F. B. Isely). 



Distribution and Ecology in Pennsylvania (See fig. 32) : This is a very common 

 form in western Pennsylvania, and is practically fovmd everywhere, both in large 

 rivers and in small creeks. It is often associated with the t^q^ical L. ovata, in the 

 large rivers, but is distinctly less abundant in these, and, as has been said, inter- 

 grades with L. ovata. In the smaller streams where typical ovata is missing it is 

 extremely abundant, and becomes at favorable localities the prevailing species. 

 It goes far up into the headwaters, eastward to McKean, Indiana, Westmoreland, 

 and Somerset Counties. It should be noted, that it is also found in Conneaut 

 Creek in the Lake Erie-drainage. 



In its ecological preferences this form differs decidedly from the normal 

 L. ovata, for it does not favor rough bottoms and currents, but rather quiet pools 

 and eddies above and below riffles. Open pools in riffles, in Di anther a-paiches, 

 with moderate current, and a bottom of fine gravel covered with a thin layer of 

 mud, seem to be most favorable habitats, and occasionally^ this form is found 

 even in pure sand and rather deep and soft mud. It is the variety of smaller 

 streams, where it is found in rather protected locations, while L. ovata is the variety 

 of the rough waters of larger streams. 



General distribution: Type locality, Wisconsin River (Barnes). 



L. ovata ventricosa is found aU over the Ohio and upper Mississippi drainages 

 in western Pennsylvania, West Virginia, Ohio (Sterki, 1907a), Indiana (Call, 

 1896a & 1900), Iflinois (Baker, 1906; Forbes & Richardson, 1913), Iowa (Pratt, 

 1876; Witter, 1878; Geiser, 1910), Wisconsin (Barnes, 1823; Cooper, 1855), and 

 Minnesota (Cooper, 1855; Grant, 1886; Holzinger, 1888). It also largely crosses 

 over into the lake-drainage in northern Illinois, Indiana, and Ohio, and occurs in 

 Michigan (Walker, 1898). In New York, it is found in the upper Allegheny- 

 drainage (Chautauqua Lake), and at many places in the St. Lawrence-drainage 

 (Marshall, 1895). That the normal form is found here is shown by specimens 

 from the Genesee River in the Carnegie Museum. In addition it has been reported 

 from the lower St. Lawrence system and its lakes (Erie and Ontario) ; but in this 

 region it is generally supplanted by the var. canadensis (See below), and since 

 this has not been separated from ventricosa by most previous authors, the mutual 

 geographical relation of these two forms is obscure. No localities from the Atlantic 

 drainage in central New York are known, and it is missing on the Atlantic slope, 

 with the exception of the upper Potomac River, where it has been introduced 



