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 lonoritudinal 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 4.60 mill. (12083.) 

 " 17.00; " 7.00; '* '' 8.50; '« 4.00 *' (12083.) 



" 16.00; '' 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. 5, 6. 



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



Limneus elongatus S&y,l. c. 167. 1821. 



Limnaea paluttris Y&T. distortus, Rossmassler, Icon. 1: 97. pi. li. f. 52. 

 1835. 



Limnaea exilis Lea, Trans. Amer. Phil. Soc. 5 : 114. pi. xix. /. 82. 1837. 

 (Variety.) 



Limnaea kirthandiaria 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; 



