OP CONCHOLOGY. 311 



DESCRIPTIONS OP NEW SPECIES OP NORTH 

 AMERICAN LAND SHELLS. 



BY THOMAS BLAN"P. 



Helix Jacksonii, no v. sp. — Plate 21, fig. 8. 



T. anguste urabilicata, depressa, nitida, fusco vel pallide 

 cornea, superne vix elevata, striata subtus coavexa, striis ex- 

 ilioribus; anfr. 6, convexiusculi, lente accrescentes, ultimus 

 antice subito deflexus, pone aperturam constrictus, superne 

 gibboso-inflatus ; sutura impressa; apertura obliqua, lunato- 

 circularis, tridentata ; perist. callosum, fusco-roseum, breviter 

 reflexurn, marginibus vix conniventibus, dente, albo, lingui- 

 formi, bicruri, profiinde intrante junctis, basali plica valida, 

 obliqua, sinuosa, dextro dente profundo immerso munito. 



Shell narrowly umbilicate, depressed, shining, dark or pale 

 horn-colored, little elevated above, striated, convex beneath, with 

 finer almost obsolete striae; whorls 6, slightly convex, gradually 

 increasing, the last suddenly deflected, contracted and above 

 gibbously inflated behind the aperture; suture impressed; aper- 

 ture oblique, lunate-circular, with three teeth; peristome 

 thickened, brownish-red, shortly reflected, with the scarcely 

 approaching margins joined by a white, linguiform, bicural, 

 deeply entering tooth, the basal margin with a strong oblique, 

 sinuous fold, the right with a deeply seated tooth. 



Dimensions. — Diam. maj. 7, min. 6, alt. 4 mill. 



Large dead specimens, brought down from the upper coun- 

 try by the streams flowing into the Arkansas River, measure: 

 Diam. maj. 9, min. 8, alt. 4 mill. 



Habitat. — Fort Gibson, Indian (Cherokee) Territory, (V. B. 

 Hubbard!) 



Remarks. — This species belongs to the same group as, and 

 is most nearly allied to H. Hazard!, Bland, (H. plicata, Say,) 

 from which, however, it may be readily distinguished by the 

 very different character of the parietal and basal teeth. This 

 species has no internal tubercle. 



