EASTERN PROVINCE — INTERIOR REGION SPECIES. 293 



cation to the inner cutting point of the transition teeth (thirteenth and 

 fourteenth teeth), at k'-ast on tlie por'tioii of tlie membrane examined by 

 me. 



Genitalia (Terr. Moll., V, Plate XV, Fig. B) as in IndentaUi, but the 

 duct of the genital bladder is of equal size tliroughout its length — an 

 unimportant, even if constant difference. 



Triodo|»i«4 introfcrcns, Bland. 



Shell und)ilicate, globose, deinesscd, thin, witli rib-like striae, yellow- 

 isli horn-colored ; spire convex ; Avhorls 0, moderately convex, the last 

 scarcely descending, ninch constricted at the aperture, with no. 315. 

 two exterior pits, subangulur at the periphery, convex be- 

 neath, grooved within the umbilicus; aperture oblique, 

 lunate, with a well-developed, arcuate parietal tooth ; peri- 

 stome white, thi(;kened within, reflected ; on the right mar- 2'. m<ro/emi«. 

 gin an obtuse, inflected tooth, at the base a submarginal, lamelliform 

 tooth, with transverse tubercle in the center; the basal lamella con- 

 tinued within the aperture, where it Ibrms a strong, white tubercle. 

 Greater diameter 15, lesser 13""" ; height, 7""". 



Belix infroferevs, Bland, Ann. N. Y. Lye, vii, 117, pi. iv, figs. 3, 4 (18G0). — W. G. 



BiNNKY, L. & Fr.-W. Sh., i, 132 (IHGO). 

 Triodopm introj'vrenn, Tuyon, Am. .Joiirn. Conch., iii, i")l (1867). — W. G. BiNNKY, Terr. 



Moll., V, 310. 



Gaston County, North Carolina ; Salem, N. C. ; valley of tlie JIol- 

 ston, Tennessee; Fanning County, Georgia ; Aiken, B.C.; George- 

 town, D. C. A species of the Cumbeiland Sid)region. 



This shell is closely allied to vultnosa and also to fallax. It differs 

 from the latter in the narrower umbilicus, which only shows the penid- 

 timate whorl; in the groo\e in the last wdiorl within the umbilical 

 opening, the character of the basal tooth, and (lie internal tubercle, 

 which does not prevail u) fallax and its immediate allies, tridenfafa and 

 Ilopetimensis. In introfercns the upper tooth is less deeply seated and 

 less inflected and the basal one is broader and more elevated than in 

 vultuoHa ; the parietal tooth is more arcuate, being iiidecHl subiingidai-, 

 but is without the indication, noticeable in vtiUuom, oi' n callus extend- 

 ing from its lower termination towards the ui)per angle of the ])eri- 

 stome. T. vultuo.sa is even smaller than the var. minor of this species, 

 which is only 11""" in diameter. 



