Baker — A Revision of the Limnaeas of Northern Illinois. 17 

 7a. Limnaea palustris michiganensis Walker. 



PI. I. f. 5. 



This form is characterized (although connected by inter- 

 mediate forms with the type) by the aperture being about one 

 half the total length, the outer lip is thickened within by a 

 bluish-white callus edged with brownish black ; this shows as 

 a white longitudinal band on the outside of the shell. Mr. 

 Walker mentions very fine spiral lines but these are as fully 

 developed in the typical forms as in the variety. 



Length 20.00; width 8.00; aperture length 9.00; width 4.50 mill. (.12083.) 

 " 17.00; " 7.00; " " 8.50; " 4.00 " (12083.) 



" 15.00; " 7.00; " " 8.00; " 4.00 '■ (12082.) 



Habitat; Associated always with the type, but not as 

 numerous in individuals. 



8. Limnaea reflexa Say. 



Pi. I. f. 3, 6. 



Limneus reflexus Say, Journ. Phil. Acad. 2 : 167. 1821. 



Limneus elongatus Say, 1. c. 167. 1821. 



Limnaea palustris var. distortus, Rossmassler, Icon. 1 : 97. pi. ii. f. 52. 

 1835. 



Limnaea exilis Lea, Trans. Amer. Phil. Soc. 5 : 114. pl.xix. f. 82. 1837. 

 (Variety.) 



Limnaea kirthandiana Lea, Proc. Amer. Phil. Soc. 2: 33. 1841. (Va- 

 riety.) 



Limnaea lanceata Gould, Proc. Bost. Soc. N. H. 3: 64. 1848. 



Limnaea zebra Tryon, Amer. Jour. Conch. 1 : 228. pi. xxiii. f. 4. 1865. 



Shell: Very much elongated, narrow, thin, sometimes 

 scalar ; color honey-yellow to black, sometimes obscurely 

 longitudinally banded; surface shining, covered with numer- 

 ous closely crowded growth lines, sometimes showing very 

 fine impressed spiral lines which reticulate the surface; the 

 growth lines are also wavy and elevated, in some specimens 

 forming elevated ridges of considerable size; apex smooth, 

 brownish or blackish ; whorls 6-7, elongate-rounded, last 

 whorl dilated (compressed in some varieties), reflexed ; spire 

 very long and pointed, occupying about two-thirds of the 

 entire length of the shell ; sutures impressed ; aperture lunate 

 or elongate-ovate, narrowed at the upper part, very oblique 

 in some specimens; peristome thin, sharp, thickened by a 

 heavy callus on the inside, the callus chocolate or purplish in 

 color; peristome whitish; lower part of peristome dilated; 



