420 THE CHICAGO ACADEMY OF SCIENCES. 



them from their rocky support, but is strong enough to carry away 

 muddy sediment brought from the thoroughfares. The colonies in 

 Square Lake live on a shore sheltered form the surf of the strong and 

 most prevailing (northwest) winds and always in a location where the 

 bottom is rocky, or sandy with stones. They are more frequently 

 found in the vicinity of an inlet or thoroughfare." (Nylander). 



REMARKS: In 1843, Mighels described and figured a large 

 Lymnsea found in Second Eagle Lake on Fish River, Aroostook Co., 

 Maine, as Limncea ampla. The shells were secured by Mr. Alexander 

 W. Longfellow (a brother of the poet Longfellow) who obtained four 

 specimens although he reported them as very common on the shores 

 of the lake. Prof. Edward S. Morse and Mr. John M. Gould collected 

 seven dead specimens in 1852. Previously to the extensive collecting 

 carried on by Mr. Olof O. Nylander of Caribou, Maine, these were 

 the only notes which had been made on this species. Mr. Nylander 

 has made a very complete survey of the waters of Fish River and the 

 adjacent lakes and the many excellent series obtained of this species 

 has led both Dr. H. A. Pilsbry and the writer to consider mighelsi a 

 variety of emarginata. 



A careful study of this magnificent material, much of it from the 

 original locality, Second Eagle (or Mud) Lake (a large portion of 

 which he has presented to the Academy of Natural Sciences of Phil- 

 adelphia and to the Chicago Academy of Sciences), has laid at rest all 

 doubts which might be entertained as to the propriety of uniting 

 mighelsi with emarginata as a race. The opinion expressed by the 

 author several years ago (Bull. Chicago Acad. Sci. II, No. 3) has been 

 amply corroborated. The Maine specimens show a perfect gradation 

 from typical emarginata to mighelsi as will be seen by comparing the 

 figures on the plates. 



It is evident, however, that the name mighelsi has been made to 

 cover many forms which should be included in other races of emar- 

 ginata, a fact made clear by the examination of a large series from 

 Wisconsin and Michigan. The race, as indicated by the original de- 

 scription and figures, has a very large, elongated aperture, and a very 

 wide, much depressed spire, quite different from the rounded aperture 

 and generally bulbous form of the specimens from Michigan and Wis- 

 consin which have been referred to mighelsi (figure Ib of Mighels 

 plate is a transition form between mighelsi and emarginata). True 

 mighelsi has been seen only from Aroostook County, Maine, and 

 Brome Lake, Quebec. In Maine it shows a perfect gradation from the 

 narrow, long spired emarginata to the wide, flat spired mighelsi. The 



