S76 A MANUAL OF AMERICAN LAND SHELLS. 



Polygyra Ariadnse, Pfr. 



Shell with an arcuate riination, terminating in a minute, oblique per- 

 foration, depressed, subdiscoidal, rather solid, nearlj^ transparent, blu 

 Fig. 411. ish-white, with scarcely perceptible wrinkles on the uppev 

 surface; spire flattened; whorls 5, separated by a distiLCL 

 suture, flattened, the last one suddenly falling towards the 

 aperture, very much contracted and pinched behind the per- 

 istome, more convex and smoother below; there is a deeply 

 chiseled, arcuated, umbilical rimation ; the umbilical region 

 is also channeled ; aperture small, extremely complicated 

 ^ith teeth, very oblique. Innately circular, ringent; peri- 

 stome white, slightly reflected, its terminations approaching each other 

 and joined by two flexuose, elevated, acute lamin.T, converging to a 

 point far within the aperture; the basal margin of the peristome is also 

 furnished with two stout, entering, converging marginal folds ; the 

 right margin of the peristome has a more delicate, deeply seated, elon- 

 gated lamina, running almost parallel with the peristome. Greater di- 

 ameter 12, lesser 10™™ ; height, 5™™. 



Belix Ariadna', Pfeiffer, in Zeitsch. f. Mai., 1848, 120 ; Mou. Hel, Viv., iii, 266; in 

 Chemnitz, ed. 2, i, 372, pi. Ixv, figs. 19-21 (1846).— W. G. Binney, Terr. 

 Moll., iv, 76, pi. Ixxviii, figs. 1,3,4; L. &. Fr.-W. Sh., i, 104, fig. 180 (1869).— 

 Fischer and Ckosse, Moll. Mex. et Guat., 287, pi. xii, fig. 8 (1870). 



Helix Couchiana, Lea, Proc. Acad. Nat. Sci. Phila., 1857, 102; Journ., — ; Obs., xi, 139, 

 pi. xxiv, fig. 112. 



Dcedalochila Ariadna', Tryon, Am. Journ. Conch., iii, 66 (1867). 



Polygyra Ariadna;, W. G. Binney, Terr. Moll., v, 280. 



In the region of the Rio Grande, both in Texas and Tamaulipas. A 

 species of the Texan Subregion. 

 Animal not observed. 



Polygyra septeinvolva, Say. 



Shell broadly umbilicated, ^ubcarinated, discoidal, russet horn-color, 

 Fig. 412. with stou stiiffi abovc, smooth below ; plane above, 



with 7 (sometimes 8^) or less flattened whorls; 

 equally plane below, with ,3^ full, more convex 

 whorls on a level, then ending in a deep, pervious 

 umbilicus, the penultimate somewhat overlapped 

 by the last, the antepenultimate much the largest; 

 aperture very oblique, remote from the axis, sub- 

 p. ««p*.„u-o^ a, enlarged, renifomi, coustrictcd behind the peristome; peri- 

 stome thickened, bluntly reflected, continuous, its terminations joined 



