LYMNJEIDJE OF NORTH AMERICA. 155 



Range: Michigan to Minnesota north of the 45th parallel of 

 north latitude. A species of the Canadian and Upper Mississippian re- 

 gions and of the Canadian and Transition life zones. 



RECORDS. 



Michigan: Isle Royale; various localities (Adams; Gleason; Walker). 



Minnesota: Lake Harriet, near Minneapolis, Hennepin Co. (Daniels). 



Wisconsin : Quynoch Point, Eagle Bay, and other portions of Tomahawk 

 Lake, Oneida Co. (Baker). 



Geological Range : Unknown. 



Ecology : Lilliance is typically an inhabitant of sandy shores, in 

 shallow water, where it is subjected to heavy wave action; only once 

 was a specimen found in a still-water habitat, and this instance was 

 undoubtedly caused by drifting from its normal habitat. When any 

 number of specimens were found, the habitat was invariably an ex- 

 posed beach. Associated with lilliance were Galba emarginata wiscon- 

 sinensis and Planorbis binneyi. Individuals were observed crawling 

 over the sandy beach or attached to water-soaked logs or other shore 

 debris. The animal of this race exhibits two color modifications, one 

 bright yellow and the other black or grayish-black. No cause for this 

 color dimorphism was apparent. It is not protective, as both forms 

 occupy the same area of white sandy beach. See the introduction, 

 (page 45) for a discussion of the breeding habits of this race. 



Remarks : Lilliance may be known by its short spire, long and 

 narrow aperture, and compressed body-zvhorl. It was at first thought 

 to be a form of sanctcemarice but a comparison with that species shows 

 it to be uniformly narrower with compressed body-zvhorl, and more 

 acute spire. In sanctcemarice the body- whorl is usually very rotund; 

 the aperture is also roundly ovate, while in lilliance it is elongate-ovate. 

 The musculature of the male organ is also quite different from sanc- 

 tcemarice, and similar to that of appressa. Lilliance differs from ap- 

 pressa in its short spire, flattened and compressed body-zvhorl and elon- 

 gated aperture. It appears to be a distinguishable race of stagnalis. 

 No true appressa were found associated with this race in Tomahawk 

 Lake. There were a few specimens with spires and aperture of equal 

 length, showing clearly that the race is a modification of the appressa 

 type, caused, doubtless, by a change of environment. 



At Isle Royale, in Lake Superior, a form of stagnalis occurs which 

 at first sight appears quite distinct. A number of individuals, how- 

 ever, approach very closely to var. lilliance and they may be referred 

 provisionally to this race. Judging from the material at hand, this 

 is a transition form between appressa and lilliance, representing, per- 

 haps, one of the stages in the evolution of the race. The Isle Royale 



