468 



MICHIGAN SURVEY, 1905. 



POLYQYRA ELEVATA (Say). 



Shell imperforate, very convex, elevated, almost coni- 

 cal; yellowish horn-color; whorls 7, rounded, finely; 

 obliquely striate, the last ventricose; suture distinct, 

 aperture contracted by the peristome, somewhat trian- 

 gular; peristome white, thickened, reflected, its basal 

 portion with an obsolete lamellar denticle; parietal wall 

 with a large, white, obliquely curved tooth. 



Fig. 17. p.eievata. (Binney.) Alt. 17, greater diam. 25, lesser 20 mm. 



Helix elevata, Say, Jour. A. N. S. P., II., 154, (1821). " 



Mesodon elevatus, W. G. Binney, Man. Am. Land Shells, 306, fig. 328, (1885). 



Helix elevata, Sager, Doc. H. Rep. Mich., 1839, 420, separate, 14. 



, Miles, Rep. Geol. Surv. Mich., 235, (1861). 



Xolotrema , Currier, Shell-bearing Moll. Mich., 5, (1868). 



, DeCamp, Shell-bearing Moll. Mich., 6, (1881). 



Polygyra , Walker, Rev. Moll. Fauna Mich., 16, (1894). 



K Very rare. Niles and Grand Rapids are the only authentic localities. It 



has been reported from Osceola County, and as fossil in recent deposits near 



Ann Arbor. 



POLYQYRA PENNSYLVANICA (Green). 



Shell imperforate, globosely elevated, yellowish horn-colored; 

 whorls 6, closely and obliquely striate; suture impressed; aper- 

 ture subtriangular; lip narrow, white, roundly reflected with a 

 jsHght thickening at the base; umbilical region indented. 



Alt. 11, diam. 18 mm. 

 Helix pennsylvanica, Green, Cont. Macl. Lye. I. 8, (1827). 

 Mesodon pennsylvanicus , W. G. Binney, Man. Am. Land Shells, 



304, fig. 324, (1885). 

 Monroe county and Bois Blanc Island, Detroit river. 



The occurrence of this species in Michigan was until the present year 

 (1906) considered extremely doubtful. It has, however, been recently col- 

 lected by Sister M. Catherine near Monroe. It is easily distinguished from 

 allied species by its striate surface, imperforate base and edentulous aper- 

 ture. 



I POLYQYRA THYROIDES (Say). 



Shell narrowly umbilicate, de- 

 pressed, globose; uniform light 

 horn or russet color; whorls 5, 

 finely and obliquely striate ; spire 

 more or less elevated; suture 

 well impressed; aperture oblique, 

 lunate; parietal wall with a 

 prominent white tooth, which is occasionally obsolete; peristome white, 

 thickened; widely reflected; its exterior yellowish; umbihcus partially cov- 

 ered by the reflected peristome. 



Alt. 13, greater diam. 22, lesser 19^ mm. 



Helix thyroidus, >Say, Jour. A. N. S. P. L, 123, (1817). 

 Mesodon thyroides, W. G. Binney, Man. Am. Land Shells, 313, fig. 

 (1885). 



Fig ]S. 



P. pennsylvanica. 



(Binney.) 



Fig. 19. P. thyroides. (Binney.) 



235, 



