OF NORTH AMERICA. 159 



RECORDS. 



UNITED STATES. 



MICHIGAN: Neebish Rapids, St. Mary's River, Chippewa Co.; Sault St. 

 Marie, Chippewa Co.; Black Lake, Presque Isle Co.; shore of Lake Superior, 

 and Siskowit Lake, Isle Royale, Lake Superior (Walker). 



BRITISH AMERICA. 



ONTARIO: Michipicoten Bay, Thunder Bay District (Brown); north shore 

 Lake Superior (Ferriss) ; Lake Superior (Newberry). 



GEOLOGICAL RANGE: Unknown. 



ECOLOGY : "Attached to the larger rocks that are not readily moved 

 by the action of the surf." (Walker and Ruthven, Isle Royale.) From 

 the records of Ruthven and Adams, this race would seem to be 

 typically an inhabitant of a region under the influence of clear, shore 

 waters in situations where there is considerable action of the waves. 

 In this respect it differs widely from stagnalis appressa, which is a 

 lover of quiet waters subject to more or less stagnation. In the St. 

 Mary's River it inhabits the Neebish Rapids, which provides an en- 

 vironment similar to that afforded by the wave action of the Lake Su- 

 perior stations. 



Sanctcemaricz exhibits beautifully the correlation of the animal 

 with its environment. In Isle Royale the form living on an exposed 

 lake beach is rather small with a thick shell. The form living in Sis- 

 kowit Bay, where the water is quiet, is the largest of any North Ameri- 

 can Lymnaa, and the shell is thin and brittle. There is usually little 

 variation in general form ; rarely a specimen occurs in which the body 

 whorl is compressed and the spire lengthened (PI. XXI, figure 2; pi. 

 XXIII, fig. 2). These forms approach some individuals of L. stagnalis 

 lilliana, but are doubtless cases of parallel development. See Chap- 

 ter II, p. 24 for a more detailed discussion of the ecological relations 

 of this race. 



REMARKS : This rather distinct race may be known by its very 

 short spire, rotund body-whorl and wide, somewhat patulous aperture. 

 It appears to be a northern race which reaches its maximum develop- 

 ment in the cold waters of Lake Superior. 



The name sanctcemaria was apparently founded on immature 

 specimens; higleyi is the fully mature form, and must fall into the 

 synonymy. Specimens from Sault Ste. Marie have a coarse dark 

 brown epidermis and many of the specimens seen by the writer appear 

 to have suffered an injury to the last third of the body whorl, which 

 is joined to the body of the shell in such a manner as to leave a deep 

 channel at the suture. This portion of the last whorl is also disposed 

 to be malleated. 



