OP CONCnOLOGY. 3tl 



DESCRIPTIONS OF NEW SPECIES OF NORTH 

 AMERICAN LAND SHELLS. 



BY THOitAS BLAN'D. 



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



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

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

 ilioribus; anfr. 6, convexiasculi, leiite accrescentes, ultiinus 

 antice subito deflexus, pone aperturani constrictus, superne 

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

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

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

 forrni, bicruri, profunde intrante junctis, basali plica valida, 

 obliqua, sinuosa, dextro dente profiindo immerso munito. 



Shell narrowly umbilicate, depressed, shining, dark or pale 

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

 finer almost obsolete striiie; 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. — -Diara. 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. 



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. Hazardi, 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. 



