ORTMANN: monograph of the naiades of PENNSYLVANIA. 151 



with typical grandis, and should be classed with them. In Lake Erie, this form 

 is found, as has been stated, under various ecological conditions, but not in the 

 open lake. It is present on the north shore of Presque Isle Bay, where there is, 

 at times, a considerable surf, and lives here in from one to five feet of water. It 

 has also been brought up by the "sand-sucker" from a depth of ten to fifteen feet. 

 It prefers a bottom of pure sand or fine gravel, either bare, or covered with a growth 

 of rushes {Juncus americanus). Many specimens on the north shore of the bay 

 are much abraded, and apparently worn by the surf. Toward the western end 

 of the bay, it is found upon the sandy "flats," among rushes, and at the extreme 

 western end on a bottom, which consists of a mixture of sand and mud; in this 

 section, the water is rather quiet, there is surf only during easterly winds, and 

 this is broken and checked by the Juncus americanus formation, which runs far 

 out into the bay. Further, this species in a special form inhabits the numerous 

 lagoons and beach-pools of Presque Isle, which are rather shallow, and have a 

 bottom of fine sand, often covered with more or less fine vegetable mud. It occurs 

 also in the large and deep lagoon at Waldamer Park (base of Presque Isle), and I 

 also found it in a pond cut off from the mouth of Elk Creek, on sandj'-gravelly 

 bottom. In Pennsylvania, this is distinctly a lake- and pond-form. 



Lake Erie and the smaller lakes of the state of Michigan seem to be the metrop- 

 oHs of this form. The largest number of locality records are at hand from Michigan, 

 due to the fine work of Walker (1898, see map of distribution, PL 1). Northwards 

 it goes here as far as Chippewa Co. (Winslow, 1917) and Marquette Co. (South 

 of Lake Superior), and Lake Gogebic, Ontonagon Co. (Ruthven). It is also in 

 the lakes and bays of Isle Royale in Lake Superior (Walker, 1909, p. 294), and the 

 Carnegie Museum possesses it from the region of Nipigon, on the North shore of 

 Lake Superior. The most extreme locality in a northwestern direction is Souris 

 River, Manitoba (Hudson Bay-drainage) (Dawson, 1875). 



From Wisconsin it is known only from the type locality (Winnebago) . South- 

 ward, it crosses over into the Mississippi-drainage in northern Ohio (Sterki, 1907a), 

 northern Indiana (Call, 1896a and 1900),'^° and northern Illinois (Cook, Lake, 

 Kane, McHenry Cos.) (See Baker, 1906, p. 73). . 



From Lake Erie eastwards and northeastwards, we have a number of records 

 in western New York (Marshall, 1895), as far as Ottawa River, Canada (Call, 

 1885). However, some of these are doubtful, as for instance, Call's record from 

 Chautauqua Lake, according to him the only locality in the Mississippi basin. 



"" As to grandis and footiana in Winona Lake (See footnote 98 on p. 144). Our specimens from this 

 lake are nearer grandis. The form from Tippecanoe Lake in our collection is more like footiana; Wilson 



it Clark (19r2n, p. 47) call this forni; grandit;, " of a more inflated type." 



