THE NATURAL HISTORY SURVEY. 273 



central tooth as usual; first four laterals with a quadrate base 

 of attachment, about as wide as high; reflection bicuspid, the 

 inner cusp very large, the outer cusp smaller; fifth to seventh 

 transitory, the inner cusp becoming split up into two cusps 

 and a smaller cusp appearing on the outer side of the outer 

 cusp; eighth, and all after true marginals, long and narrow, 

 with from five to seven cusps; at first two of the cusps are 

 situated some distance up the outer margin of the cusp, but 

 finally (20) they appear only on the distal end (Fig. 88). 

 Genitalia: Not examined. 

 Distribution: Same as caperata. 

 Geological distribution : Pleistocene; Loess. 

 Habitat: Similar to and almost always associated with 

 caper ata. 



Remarks: This variety was formerly identified as cubensis 

 Pfr., but that species has a smooth shell and is more robust, 

 grouping with humilis and desidiosa rather than with the caperata 

 section. Umbilicata is doubtless a form of caperata, but seems 

 distinct enough to constitute a separate variety characterized 

 by a short spire and swollen whorls. Like caperata, the variety 

 is universally distributed throughout the area, but is not quite 

 so common. Fossil specimens have been found in sand banks 

 along the lake shore north of Graceland avenue. 

 no. Limnsea palustris Muller, pi. xxxii, fig. 1. 



Limncea palustris MULLER, Zool. Dan. Prodr., 2934, 1776. 



Limnceus elodes SAY, Journ. Phil. Acad., Vol. II, p. 169, 1821. 



Limncea umbrosa SAY, Amer. Conch., pi. xxxi, fig. 1, 1832. 



Limncea plebeia GOULD, Invert, of Mass., 1841. 



Limncea fragilis HALDEMAN (non Linne), Mon. p. 20, pi. vi (non figs. 



10, 11), 1842. 



Limncea sumassi BAIRD, Proc. Zool. Soc., London, p. 68, 1863. 

 Limncea palustris var. zebra J. W. TAYLOR, British Mollusca (vide 

 Walker, in letter). 



Shell: Varying from elongate to elongate-ovate, rather 

 thin; color varying from pale brown to almost jet black; sur- 

 face dull to shining, covered with numerous crowded growth 

 lines crossed by several elevated spiral lines and by numerous 

 very fine impressed spiral lines, which give the surface a mal- 

 leated aspect; the whorls are sometimes encircled by coarse 

 wrinkles, and frequently the epidermis is so arranged as to 

 show longitudinal stripes of white and horn color, alternating; 

 whorls six, rounded, the last varying in its rotundity; spire 

 sharp and pointed, varying from over half to three-fifths the 



