20 



THE NAUTILUS. 



long, ovate, much narrowed above, generally wide and flaring below; 

 outer lip with variceal thickening; inner lip rather broad, reflected 

 over the umbilical region, forming a conspicuous expansion and leav- 

 ing 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 33.50, breadth 13.00; aperture length 14.00, breadth 

 7.00 mm. 



Length 29.00, breadth 13.00; aperture length 15.00, breadth 

 6.75 mm. 



Length 28.75, breadth 13.50; aperture length 15.75, breadth 

 7.00 mm. 



Length 25.00, breadth 12.00; aperture length 14.00, breadth 

 7.25 mm. 



Length 21.00, breadth 10.00; aperture length 12.00, breadth 

 6.00 mm. 



Length 24.00, breadth 10.00; aperture length 11.00, breadth 

 5.00 mm. 



Length 18.25, breadth 8.25; aperture length 10.00, breadth 

 4.25 mm. 



Types: The Chicago Academy of Sciences, 9 specimens. No. 

 24539 ; cotypes, Academy of Natural Sciences, Philadelphia, No. 

 98521, 6 specimens. 



Type locality: Marl beds, Nashotah, Waukeshaw County, Wis- 

 consin. 



Remarks: L. nashotahensis was at first thought to be a form of 

 Lymneea danielsi ; it differs markedly from that species, however, in 

 several particulars — the spire is broader and not so acute, the body 

 whorl is larger and inclined to be gibbous, there is a conspicuous 

 umbilical chink (^danielsi is usually imperforate), and the columella 

 is not noticeably plicate. In nashotahensis the aperture is elongate 

 ovate, narrowed above and broadened below, where it is often patu- 

 lous. The upper whorls are strongly suggestive of Lymnaa rejlexa, 

 the penultimate whorl having the swollen appearance so characteristic 

 of rejUxa. 



Young specimens somewhat resemble Lymncea catascopium, differ- 

 ing in being narrower, with a more elongate aperture, longer and less. 



