^06 



MICHIGAN SURVEY, 1905. 



STROBILOPS LABYRINTHICA (Say). 



Shell umbilicated, elevated conoidal, brown 

 ish horn-color, with strong ribs above, below 

 almost smooth; spire obtuse; whorls wider than 

 high, regularly increasing in size from apex to 

 aperture; body-whorl obtusely angulated at the/ 

 Fig. 119. s. labyrinihica. X8.4. periphery, flattened below, impressed around 

 the narrow umbilicus; aperture rounded above, basal margin flattened, 

 peristome narrowdy reflected, thickened; parietal w^all with three revolving, 

 deeply entering parallel lamellse, the central further within the aperture and 

 less developed, one conspicuously emerging from the aperture; two to four 

 short, internal lamellse on base of body whorl. 



Alt. If, greater diam. 2^ mm. 

 Helix lahyrinthica, Say, Jour. A. N. S. P., I., 124, (1817). 

 Strohila 



Helix 



Strohila 



W. G. Binney, Man. Am. Land Shells, 264, fig. 281, 

 (1885). 



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



Currier, Shell-bearing Moll. Mich., 4, (1868). 



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



.Strobilops — , Walker, Rev. Moll. Fauna Mich., 17, (1894). 



Apparently rare in this state. Bay, Saginaw, Kent, Kalamazoo and Ber- 

 rien counties are the only localities reported. 



This species is easily to be distinguished from both virgo and affinis, not 

 only by the constant difference in the number and situation of the internal 

 lamellse, but by the depressed form, more conical spire, stronger ribs and 

 flattened base; viewed from above the whorls are noticeably wider than in 

 either of the other species and the peripheral angle is much stronger. Its 

 general appearance is that of a lower, wider shell than either of the other 

 species. 



STROBILOPS VIRQO (Pilsbry). 



Shell umbilicated, globosely elevated; white 



or pale brownish color; flnely and closely ribbed 



above, ribs sub-obsolete on the base; spire high; 



dome-shaped; whorls 5^, narrow, about as 



high as wide, body whorl somewhat angled at 



the periphery, rounded below, impressed around 



the umbilicus which is a mere perforation; ap- 



Fig. 120. S.Virgo. x8.4. erture Innately rounded; peristome narrow, 



thickened, reflected; two parietal folds conspicuously emerging; 6 long 



lamellae on the base and outer wall of the body whorl. 



Alt. 2, greater diam. 2^ mm. 



Strohila lahyrinthica virgo, Pilsbry, Naut. VI., 94, 1892. 

 Strohilops virgo, Pilsbry, Naut. VII., 56, (1893). 



; Walker, Rev. Moll. Fauna Mich., 17, (1894). 



The only species yet reported from the northern part of the state, where 

 it is quite abundant. South of Iosco county, the only localities reported are 

 in Oakland, Saginaw and Kalamazoo counties. 



Aside from the peculiar arrangement of both the internal and parietal 

 lamellse, virgo is easily separated from lahyrinthica by its rounded dome- 

 shaped spire, finer ribs, rounder aperture, and more convex base and less 

 accentuated peripheral angle. 



