510 



MICHIGAN SURVEY, 1905. 



bh. Shell cylindrical, last whorl not wider than the penultimate, pari- 

 etal and inferior palatal teeth curved pentodon. 



aa. Aperture not thickened within, no labial teeth corticaria. 



Section ALBINULA Sterki. 



Throat nearly closed by teeth. Shell oblong or conic, rather wide; pari- 

 etal and calumellar lamellse long and tortuous, the latter more or less ver- 

 tical; palatal folds several, situated on a ridge. 



BIFIDARIA ARMIFERA (Say) 



Shell cylindrical, smooth; whorls 6-7, convex, apex rather 

 obtuse; suture impressed; peristome white, thin, subre- 

 flected, forming the whole outline of the aperture, its ex- 

 tremities connected by a callus deposit on parietal wall; 

 aperture oval, deep, cup-shaped, and narrowing toward the 

 throat; parietal lamella large, irregular, with one or two 

 sharp projecting points, and is sometimes bifid; columellar 

 lamella thick, massive and situated deep in the throat; 

 palatal folds two, situated on the base of the aperture; base 

 of shell from umbilicus to margin compressed, forming a 

 short and obtuse keel; umbilicus a little expanded and 



"^"■'■(klL^TxiTBlightly perforate. 

 Alt. 4§, diam. 2§ mm. 



Pupa armifera, Say, Jour. A. N. 8. P., II., 162, (1821). 



, W. G. Binnev, Man. Am. Land Shells. 325, fig. 352, 



(1885). 



, Miles, Rep. Geol. Surv. Mich., 236, (1861). 



Leucochilla , Currier, Shell-bearing Moll. Mich., 6, (1868). 



, DeCamp; Shell-bearing Moll. Mich., 7, (1881). 



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



Generally distributed in the southern part of the state. Easily distin- 

 guished from B. contracta, which is the only species resembling it in the form 

 of the aperture, by its greater size and the arrangement of the apertural 

 lamellae. 



BIFIDARIA CONTRACTA (Say). 



Shell subconical, white, whorls 5-6, ver}" 

 convex, diminishing regularly from the 

 last whorl to the apex; suture well im- 

 pressed; peristome white, somewhat re- 

 flected, its extremities connected by a 

 raised testaceous fold making the margin 

 of the aperture entire; aperture rather tri- 

 angular, expanded above and diminishing 

 regularly into a very narrow throat; la- 

 mella^ four; parietal, large, 'coarse and ir- 

 regular, projecting into the aperture; su- 

 perior palatal fold not large, tuberculous 

 and placed near the margin of the peris- 

 tome, the inferior palatal large, deeply 

 seated near the base, the columellar la- 

 mella large and massive and deeply seated 



Fig. 133. B. contracta. (Binney.) 



