480 



MICHIGAN SURVEY, 1905. 



Section QLYf>HYALINA Von Martens. 

 Upper surface of the shell marked with sharply defined, radial impressions. 



VITREA INDENTATA (Say). 



Shell imperforate, flattened, thin, pellucid; epidermis highly 

 polished, corneous; whorls rather more than 4, rapidly enlarging, 

 with regular, subequal distant, radiating, impressed lines, which on 

 the body Avhorl extend to the centre of the base, outer whorl ex- 

 panding toward the aperture; suture well impressed; aperture 

 rather large, transverse; peristome simple, acute, very thin, at its 

 ^inferior extremity terminating at the centre of the base of the shell ; 

 (Binney.) umbilicus none, but the umbilical region is indented. 

 Alt. 2^, greater diam. 5, lesser 4^ mm. 

 Helix indentata, Say, Jour. A. N. S. P., II., 372, (1822). 

 Zonites indentatus W. G. Binney, Man. Am. Land Shells, 62, fig. 15, (1885). 



Helix indentata. 

 Hyalina indentata 



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



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



DeCamp, Shell-bearing Moll. Mich., 5, (1881). 



Zonites indentatus, Walker, Rev. Moll. Fauna Mich., 16, (1894). 



Generally distributed in both peninsulas but not as common as either 

 V. hammonis or Z. arhorea. Distinguished by the impressed radiating lines 

 and imperforate base. 



VITREA RHOADSI Pilsbry. 



Shell umbihcate, depressed, thin, pellucid, corneous; surface pohshed with 

 numerous impressed radiating lines; whorls about 4, rapidly enlarging, suture 

 impressed, aperture rather large, transverse; lip simple, acute. 



Fig. 49. V. rhoadsi. Xoh 



Alt. 2^, diam. 4.8 mm. 



Vitrea rhoadsi, Pilsbry, Naut. XII., p. 101, (1899). 



This recently described species resembles V. indentata in the impressed 

 radiating lines, which sculpture the surface, but differs in being distinctly 

 umbilicated. It has thus far been reported only from the Grand Traverse 

 region at Charlevoix, Petoskey and Carp Lake, Emmet county. 



Section PARAVITREA (Pilsbry). 



Shell depressed or discoidal, perforate or narrowly umbilicate, composed 

 of numerous closely coiled whorls, usually grooved radially above; thin and 

 fragile; internally having obliquely radial laminae or rows or pairs of teeth at 

 intervals of a third of a whorl, some or all of them often wanting, especially 

 in old individuals. 



