192 -THE CHICAGO ACADEMY OF SCIENCES. 



ginal teeth aculeate. The teeth are similar in type to those of 

 the Zonitidse. 



Genitalia: Genital bladder "small, oval, on a long, deli- 

 cate duct, from about the middle of the length of which there 

 is a connecting duct to the middle of the penis sac and a second 

 duct to the apex of the dart sac." Penis long, large near the 

 vagina, "tapering above, and furnished below its apex with an 

 accessory, short, delicate, cylindrical gland, terminating in a 

 small pyriform bulb. The dart is long, delicate, strictly arrow- 

 shaped with pointed, enlarged head and much thickened at 

 the posterior termination. The penis sac is stout, short, re- 

 ceiving at its apex the vas deferens, on the commencement of 

 which the retractor muscle is inserted."* 



Distribution: Ontario, Canada, to Michigan, south to In- 

 dian Territory, Louisiana, Virginia and Tennessee. (Pilsbry.) 



Geological distribution: Pleistocene of the Mississippi Val- 

 ley; Loess. 



Habitat: Found rather sparingly in moist situations near 

 bodies of water of greater or lesser size. Prefers the under 

 side of old logs and the depths of dead brush heaps. 



Remarks: Easily recognized by its globose form, some- 

 what elevated spire and deeply impressed base. It is not a 

 common species, and, so far as known, is confined to the south- 

 ern region, about the chain of lakes. 



74. Gastrodonta demissa Binney, pi. xxviii, fig. 6. 



Helix demissa BINNEY, Bost. Journ. Nat. Hist., Vol. IV, p. 361, pi. 

 xvi, fig. 16, 1843. 



Gastrodonta demissa brittsii PILSBRY, The Nautilus, Vol. XI, p. 132, 

 1898. (Variety.) 



Shell: Umbilicated, depressed, convex; epidermis as in 

 ligera; whorls six, covered with coarse, closely crowded, trans- 

 verse striae, disappearing on the base; umbilicus small, round, 

 deep; umbilical region impressed; suture impressed; aperture 

 transverse, oblique, the base of the last whorl with a deposit as 

 in ligera; peristome thin, acute; spire very much depressed, so 

 that all the whorls cannot be seen when viewed laterally; base 

 of shell flat, smooth; last whorl but little expanded toward 

 the aperture. 



Greater diameter, 8.50; lesser, 7.25; height, 4.00; umbilicus diameter, 

 0.50 mill. (8459.) 



Animal: Not differing in general form from ligera; color 



*\V. G. Binney, Man. Am. Land Shells, p. 214. 



