[43] 



DESCRIPTIONS OP NEW SPECIES OF NORTH 

 AMERICAN I AND SHELLS. 



BY THOMAS BLAND. 



Helix Jacksonii, nov. sp. — Plate 21, fig. 8. 



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

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

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

 antice subito deflexns, pone apertiiram constrictus. superne 

 gibboso-inflatns ; sutura impressa ; apertnra obliqua, liinato- 

 circularis, tridentata : perist. callosnm, fusco-roseum, breviter 

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

 formi; bicruri, profunde intrante junctis, basali plica valida, 

 obliqiia. sinuosa, dextro dente profundo immerso mnnito. 



Shell narrowly nmbilicate, depressed, shining, dark or pale 

 born-colored, little eleyated 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. 



D ime/is ions. —Disim. maj. 7, min. 6, alt. 4 mill. 



Large dead specimens, brought down from the upper coun- 

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

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



Sabitat. — Fort Gibson, Indian (Cherokee) Territory, (Y. B. 

 Hubbard!) 



Remarlcs. — This species belongs to the same group as. and 

 is most nearly allied to R. Hazardi, Bland, [H. jAicata, 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. 



