THE NATURAL HISTORY SURVEY. 141 



"Shell: Helicoid, varying from globose or depressed-glo- 

 bose to lens-shaped or planorboid, the periphery carinated or 

 rounded; umbilicus either open or closed. Surface striated or 

 hirsute; corneus, yellow or brown, generally unicolored, but 

 sometimes with many bands, the most constant being supra-periph- 

 eral the others when present being wholly indefinite in number 

 and position. Lip well reflexed; aperture typically obstructed by 

 the teeth, one parietal, two upon the lip; but any or all teeth often 

 wanting" 



"Animal: (Fig. 14). Externally as in Helix, the mantle 

 subcentral, foot rather long and narrow, not distinctly tripartite 

 beloiv, and without longitudinal grooves above the lateral mar- 

 gins, although a sort of foot-margin is produced by the tessel- 

 lated granulation of the edge. Surface rather coarsely irregu- 



FIG. 14. 

 Animal of POLYGYRA. (After Binney.) 



larly granulated, the granulation finer posteriorly; back with 

 a pair of indistinct grooves extending from mantle to facial 

 area; sides of foot, and sides and top of tail without any distinct ob- 

 lique or longitudinal lines, irregularly granulated; tail rounded 

 above, obtuse behind. Mantle edges reflexed to correspond 

 with the lip of the shell, its edge even; shell lappets none; 

 body-lappets small, the right one long, giving off a short as- 

 cending branch behind the lung-pore; left lappet very small, 

 short." 



1 ' Genitalia : Completely lacking accessory otgans; retractor and 

 vas deferens inserted at the apex of the penis. Spermatheca 

 oval or oblong, situated upon a short simple duct. The penis is 

 divided internally into two parts; (l) a lower, invertible por- 

 tion, the inner surface of which shows few or many longitudi- 

 nal folds, which are smooth and may be either weak or strong 

 and acute; and (2) an upper portion the cavity of which has 

 finely corrugated walls and is partly filled by one or two fleshy 

 pillars adherent along the sides."* (Fig. 15.) 



*Pilsbry, Guide to Helices, pp. 69 and 70; see also Proc. Phil. Acad. 1892, p. 400. 



