LYMN,CIDy OF NORTH AMERICA. 427 



GEOLOGICAL DISTRIBUTION : Unknown. 



ECOLOGY: In Tomahawk Lake, Wisconsin, this species is very 

 abundant, the shore after storms being literally paved with dead shells. 

 It lives on the sandy or pebbly shores, in water from a few inches to 

 several feet in depth. By wading along the beach thousands may be 

 collected. The localities in this lake are all on exposed points or in 

 curved bays where the shore receives the full force of the waves. 

 No specimens were found in sheltered places, where the water was 

 at all stagnant. As recorded by Dr. Kirkland, for angulata, they were 

 irregularly scattered over the surface, crawling over the sand, where 

 a distinct track was left, or else lying half buried in the sand. The 

 two different colors mentioned by Nylander as being characteristic of 

 the Maine emarginata were also observed in the Tomahawk Lake speci- 

 mens. 



REMARKS: This race differs from all the other races of emar- 

 ginata in its very globose body whorl and rounded aperture. The race 

 is very variable, the variant being the spire which is elongated or de- 

 pressed. Some individuals approach mighelsi but this is rare, the shell 

 being usually much more globose than that race. Angulata differs in 

 having a heavier shell, a much less globose body whorl, and an elon- 

 gated and angulated, instead of rounded, aperture. The umbilicus is 

 closed in angulata while it is usually open in wisconsinensis. The glo- 

 bose form will, however, separate this race from all others. The um- 

 bilical chink is usually conspicuous but may be so wide as to form 

 a deep umbilicus or may be entirely closed. 



Wisconsinensis is by far the most abundant shell in Tomahawk 

 Lake, Wisconsin, where, in many places, it forms windrows of dead 

 shells on the shore after a northwesterly storm. It was at first thought 

 to be a variety of the mighelsi type of shell, but the globular form of 

 the body whorl is so different from mighelsi and the shells are so 

 numerous in the original locality as to render it quite as eligible to re- 

 ceive a name as are any of the races of Lymnsea. 



Galba emarginata canadensis (Sowb.). Plate XLIV, figures 

 19-23; plate XLV, figures 1-20. 



Limnaa canadensis SOWB., Conch. Icon., XVIII, Limn., sp. 45, pi. 7, figs. 

 45 a, a, 1872 (not a, b, as stated on plate). DALL, Alaska Moll., p. 69, 1905. 



Limnea emarginata DEKAY, Zool. N. Y., p. 73, pi. 4, fig. 77, 1843 (part). 

 ?KENNICOTT, Trans. 111. State Ag. Soc., I, p. 595, 1855. HENDERSON, Nautilus, 

 XX, p. 98, 1907. 



Lymncea emarginata LINSLEY, Amer. Journ. Sci., XLVIII, p. 282, 1845. 

 LEWIS, Proc. Phil. Acad., pp. 18, 19, 1860; Amer. Journ. Conch., VI, p. 86, 



