THE NATURAL HISTORY SURVEY. 337 



Amnicola cincinnatiensis BINNEY, L. and F. W. Sh., N. A., p. 85, fig. 

 169, 1863. 



Shell: Small, globose, rather solid ; 'color, different shades 

 of green; surface smooth, polished, lines of growth very faint; 

 sutures well marked; apex very obtuse, comprising one and 

 one-half whorls; when viewed from the front the shell appears 

 to have a truncated spire; spire very broadly truncate-conic; 

 whorls four to four and one-half, very convex; aperture nearly 

 round, appressed to the body-whorl; peristome continuous, 

 rather thick, simple; base rounded, with a small umbilicus. 



Length, 4.00; width, 2.00; aperture length, 1.50; width, 1.10; mill. (10241.) 

 3.25; " 1.75; " " 1.50; " 1.10; " (10241.) 



Animal: Not examined. 



Radula: 'Not examined. 



Distribution: New York west to Iowa and Winnipeg, Can- 

 ada, south to Kentucky. 



Geological distribution : Pleistocene. 



Habitat: In rivers and ponds, on a muddy bottom. 



Remarks: This species at first sight might be taken for 

 A. lustrica, but the spire is very obtuse, while that of lustrica is 

 acute, and the last whorl is appressed to the body-whorl, at the 

 aperture in obtusa, while in lustrica it is entirely free. The 

 species seems to be very rare, and living specimens have been 

 found only in the DuPage River. It has been collected on 

 the recent beach in a subfossil condition. Several dead speci- 

 mens were obtained in the North Branch of the Chicago River 

 and in beach drift at Miller's, Ind. 



GENUS PALUDESTRINA Orbigny. 



Bythinella Moquin-Tandon. 



Shell: Small, elongately-ovate, smooth and shining, with 

 an elevated spire; sometimes decidedly pupiform, rimate or 

 imperforate; apex generally obtuse; aperture ovately-rounded; 

 peristome continuous, outer lip thickened. Operculum corne- 

 ous, the nucleus large and placed rather near the basal margin. 



Animal: With a narrow foot which is rounded behind; 

 tentacles tapering to a blunt tip; verge bifid; lingual dentition 

 (of B. nickliniana) ; rhachidian tooth nearly as wide as long, 

 with the lower lateral angles very much produced, basal teeth 

 two in number, situated one on each side, reflected portion 

 seven-denticulate; intermediate tooth much longer than broad, 



