34 GASTROCOPTA, NORTH AMERICA, WEST INDIES. 



55. Bifidaria tappaniaom (C. B. Ad.) PILSBRY and VANATTA, 

 Nautilus, xix, 1906, p. 126, pi. 7, figs. 42-53. WALKER, Occ. 

 Pap. Mus. Zool. Univ. Mich., No. 15, 1915, pp. 7-11. Pupa 

 pentodon f. curia STERKI, Land and Fresh- Water Mollusca in 

 the Vicinity of New Philadelphia, 1894, p. 5; Nautilus, xix, 

 1906, p. 134. 



The shell is larger than pentodon, markedly conic though 

 obtuse ; only one tooth on the parietal wall, usually 6 on the 

 columellar, basal and outer margins, those on the latter stand- 

 ing on a strong rib. Lower palatal tooth usually not so long 

 and entering as in B. pentodon. 



Length 2, diam. 1.2 mm. 



Length 1.7, diam. 1.1 mm. 



It is rather a common species in central Arizona, the west- 

 ernmost locality being Jerome, Yavapai Co., a little west of 

 the 112th meridian. Southward it has been found near the 

 Mexican boundary in the Huachuca Mountains (Tanner 

 canyon, 6000 ft.). 



While it must be admitted that occasional individuals are 

 intermediate between tappania-n-a and pentodon, yet the two 

 forms are quite readily separable in the great majority of 

 lots. They differ in station, tappaniana being found in low, 

 moist places, under wood, often with Vertigo ovata, while 

 pentodon lives in dryer situations, as Dr. Sterki has noted. 

 G. tappaniana is not known from the southern Atlantic states, 

 Virginia to Florida, but its range extends to the Gulf of 

 Mexico in Alabama. 



G. pentodon was long known as Pupa curvidens, and G. 

 tappaniana as P. pentodon. In Binney's several publications 

 the two are united under P. pentodon, the wood-cut repre- 

 senting tappa,niana. 



Form curia, Sterki. "Examples from wet places are small 

 and short ovoid." New Philadelphia, Ohio. 



Fig. 9 of pi. 3 is from Falls of Schuylkill, West Philadel- 

 phia. The figures on plate 5 represent shells from the fol- 

 lowing localities: 



Fig. 42. School Lane, Germantown, Philadelphia, Pa. R. 

 Walton. No. 58250. 



