MOLLUSCA OF MICHIGAN— WALKER. 477 



KEY TO THE SPECIES OF VITREA. 



I. Body-whorl with two or three rows of internal teeth Multidentata. 



II. No internal teeth in body-whorl. 



a. Surface with impressed, radiating lines. 



b. Imperforate or nearly so ; indentata. 



bb. Umbilicate rhoadsi, 



aa. Surface with microscopic revolving lines. 



b. Body-whorl rapidly widening toward the aperture, base flattened, 

 spire subplanulate, brownish horn-colored, diameter 5 mm. 



wheatleyi. 



bb. Body-w^horl regularly increasing, spire slightly elevated, base rounded, 



light steel gray, diameter 2^ mm ferrea. 



aaa. Surface smooth, polished. 



b. Diameter exceeding 10 mm., base bluish-white, thickened within 



cellaria. 



bb. Diameter 4-5 mm. No basal thickening. 



c. Umbilicus small, dark horn-colored hammonis, 



cc. Umbilicus wider, almost colorless binneyana. 



Section VITREA s. s. 

 Shell smooth and polished; spiral lines, when present, very minute. 



VITREA CELLARIA (Muller). 



^'^j>^Mmi Shell very much depressed, thin, fragile, pellucid; greenish 

 horn-color above, paler beneath, smooth, highly polished; whorls 

 5, slightly rounded; aperture oblique, transverse, umbilicus 

 moderate, regularly rounded, deep; base rounded, thickened 

 within by a testaceous, bluish- white deposit; peristome simple, 

 acute. 

 Fig 41. V. eel- Alt. 5, greater diam. 13, lesser 11^ mm. 



laria (Binney.) ' ^ 



Helix cellaria, Muller, Verm. Hist., II., 28, (1774). 



Zonites cellarius, W. G. Binney, Man. Am. Land Shells, 448, fig. 493, (1885). 



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



A European species that has been locally introduced with foreign plants 

 and is usually found in quantiites where it occurs. Reported from Detroit, 

 Alma, Gratiot county, Bay City and Muskegon. Easily distinguished from 

 allied species by its larger size and the callus deposit within the aperture, 

 which renders the base opaque and bluish- w^hite. 



VITREA HAMMONIS (Strom). 



Shell narrowly umbilicated, small, depressed-conic, thin, fragile; 

 pale or brownish horn-color, wTinkled, shining; w^horls 4 the last 

 rapidly enlarging toward the aperture; aperture transversely rounded; 

 peristome simple, its edge rather thickened, not acute; base rounded. 

 v.himmonis Alt. 2, greater diam. 5, lesser 4§ mm. 



(Binney.) 



