THE NATURAL HISTORY SURVEY. 357 



growth numerous, fine, crowded, crossed by delicate spiral 

 lines; beneath the green or black epidermis the shell is pure 

 white; apex always eroded in old specimens but in young ones 

 showing a small, round, sunken nucleus, which is light horn 

 color; spire generally depressed, short, conic; sutures well im- 

 pressed; whorls six, rounded, bulbous or inflated, the last 

 whorl very large, equaling over half the length of the entire 

 shell; aperture elongately-ovate, rounded below and con- 

 tracted above, where it is produced into a sort of canal; aper- 

 ture bluish-white within; peristome sharp, thick, simple, mar- 

 gined with black; columellar lip covered by a thin coating of 

 callus, which is bordered with black and which makes the peri- 

 stome entire, joining the terminations; base of shell rounded, 

 imperforate. 



Length, 21.50; width 15.00; aperture length, 13.50; width, 8.00 mill. (8848.) 

 18.00; " 13.50; " " 13.00; " 8.00 " (8848.) 



Animal: Not examined. Operculum longer than wide, 

 much narrowed above, convex, horny, thin on the edges, sub- 

 concentric; the nucleus near the left margin; reddish brown 

 in color. Length 12.50, width 7.00 mill. (Shell 21.50 mill, long.) 



Radula: Not examined. 



Distribution: New York west to Illinois, south to Ala- 

 bama and Texas. 



Geological distribution: Pleistocene; Loess. 



Habitat: In the larger rivers on a muddy bottom. 



Remarks: Distinguished by its heavy, solid shell and 

 peculiar channeled aperture. The species is not generally 

 known to inhabit this region, being usually found farther 

 south, but the specimens before the writer are certainly pon- 

 derosum and they were said to have been collected in the Calu- 

 met River some years ago by Dr. J. W. Velie. The specimens 

 were sent to Prof. R. Ellsworth Call, the well-known student 

 of this intricate genus, who wrote as follows concerning them: 

 "The specimens are certainly Campeloma ponderosum, mostly 

 juniors, and one about two-thirds grown. They are typical of 

 that form. I seriously question that your collector found 

 them in the place indicated. It will be very interesting indeed 

 to have this settled by additional specimens, which will be the 

 only proof beyond doubt." The region has been very care- 

 fully searched for additional specimens but up to the present 

 time none have been found. It has been admitted to this list 



