476 



MICHIGAN SURVEY, 1905. 



Fig. 36. Dentition of V. limpida (Binney.) 



Q) 



VITRINA LIMPIDA Gould. 



Shell imperforate, globosely depressed, thin, fragile, transparent^ 

 shining; whorls 2^-3; scarcely convex, with very minute lines of 

 increase, the last whorl large and very much expanded; suture not 

 Fi.e; 37. much impressed, aperture large, subovate, peristome thin and 



(Binney.)' aCUte. 



Alt. 3, diam. 6 mm. 

 Vitrina limpida, Gould, Agassiz's Lake Superior, 243, (1850). 



, W. G. Binnev, Man. Am. Land Shells, 177, fig. 170, (1885). 



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



A northern species, reported from Isle Royale, Ontonagon county, Lime 

 Island in the St. Mary's river, Charlevoix, Traverse City, and Crystal Lake, 

 Benzie county. 



Genus VITREA Fitzinger. 



Shell small, thin, fragile, shining, hyaline, smooth, convexly depressed, 

 last whorl not descending at the aperture, umbilicate or 

 imperforate; aperture lunate; peristome thin and sharp. 

 Animal black or bluish-black on the upper parts, lighter, 

 \mmaAVf v^^ceiiaria Sometimes wholly white posteriorly. Foot long and narrow. 

 (Binney.) ' Jaw arcuatc, ends attenuate, pointed or rounded; con- 

 cave margin with a median rounded projection. Dentition as in Omphalina, 



Fig. 39. Jaw of V. cellarici. (Binney.) Fig. 43. Dentation of V. cellaria. (Binney.) 



KEY TO THE SECTIONS OF VITREA. 



I. No internal teeth. 



a. Surface smooth, spiral lines, when present, very minute. . .Vitrea s. s. 

 aa. Surface minutely striate, retriculated with impressed, spiral 



lines Striatura. 



aaa. Surface with sharply defined, impressed, radial lines Glyphyalina. 



II. With internal, radial rows of teeth Paravitrea. 



