108 THE CHICAGO ACADEMY OF SCIENCES. 



REMARKS: "This remarkable species was dredged from the 

 marl bottom of Pine Lake. No living specimens were found, and in 

 all probability it is extinct. In its external characteristics it is more 

 nearly related to L. jayi Dunker (gracilis Jay) than to any other of the 

 described species, but the resemblance is a general one only, the two 

 species differing in nearly every detail. The continuous, free lip and 

 straight columella are exceedingly like those of jayi, and would nat- 

 urally cause it to be referred to the subgenus Acella. But the axis is 

 not gyrate, as in that group, but is rounded and without a fold, as in 

 Galba. 



"The young shell is subcylindrical, and with its heavily shouldered, 

 turreted whorls and narrow aperture reminds one of the curious L. 

 contracta Currier from Houghton Lake. I take pleasure in dedicating 

 this very peculiar species to Mr. Frank C. Baker, of the Chicago Acad- 

 emy of Sciences, who has made a special study of the North Ameri- 

 can Lymnaeas." 



Galba nashotahensis (Baker). Plate XLVI, figures 18-24. 

 Lymn&a nashotahensis BAKER, Nautilus, XXIII, p. 19, June, 1909. 

 SHELL: Elongated, somewhat pyramidal; surface dull, growth 

 lines conspicuous, crossed by fine impressed spiral lines; whorls 6- 

 6 l / 2 , rather rapidly increasing in diameter, flatly rounded, the body 

 whorl very large and quite convex, or even gibbous ; spire broadly 

 pyramidal or conic, longer than the aperture; sutures well marked; 

 aperture elongate ovate, much narrowed above, generally wide and 

 flaring below ; outer lip with varical thickening ; inner lip rather broad, 

 reflected over the umbilical region, forming a conspicuous expansion 

 and leaving a well marked umbilical chink; parietal callus wide and 

 rather thick, in some specimens rendering the aperture continuous ; axis 

 twisted; the columella is plicate in the immature shell but in adult or 

 old specimens the inner lip is raised over the umbilicus, somewhat as 

 in emarginata. 



Length. -Breadth. Aperture Length. Breadth. 



33.50 13.00 14.00 7.00 mill. 



29.00 13.00 15.00 6.75 " 



28.75 13.50 15.75 7.00 " 



25.00 12.00 14.00 7.25 " 



21.00 10.00 12.00 6.00 " 



24.00 10.00 11.00 5.00 " 



18.25 8.25 10.00 4.25 " 



TYPES: The Chicago Academy of Sciences, 7 specimens, No. 

 24539 ; Cotypes, Academy of Natural Sciences, Philadelphia. 

 HORIZON: Pleistocene Marls of Wisconsin. 



