98 



LAND AND FRESH-WATER SHELLS OF N. A. [PART I. 



ana. H. troostiana has a slight groove on the inner side of the 

 last whirl, the absence of which in fastigans is noticed by Say, 

 but I scarcely consider that a good specific character. Fresh 

 specimens of H. fastigans are, I believe, covered with a very 

 thin epidermis, on which hairs are sparingly scattered — the scars 

 of the hairs may be detected, especially on the last whirl, in 

 denuded shells. 



Helix sacksonii, Bland. — Shell narrowly iimbilicate, depressed, 

 shining, dark or pale horn-colored, little elevated above, striated, convex 

 beneath, with finer almost obsolete striae; whirls six. 

 Fig. 174. slightly convex, gradually increasing, the last suddenly 



deflected, contracted and above gibbonsly inflated be- 

 hind the aperture ; suture impressed ; aperture oblique, 

 lunate-circular, with three teeth ; peristome thickened, 



^^ brownish-red, shortly reflected, with the scarcely ap- 

 proaching margins joined by a white, linguiform, bi- 

 crural, deeply entering tooth, the basal margin with a 

 Helix jacksonii. strong, oblique, sinuous fold, the right with a deeply 

 seated tooth. Greater diam. 7, lesser 6 ; height 4 mill. 

 Helix jacksonii, Bland, Am. Journ. Conch. II, 371, pi. xxi, f. 8 (1866). 

 Dcedalochila jacksonii, Tkyo^, Am. Journ. Conch. Ill, 67, pi. x, f. 32, 33, 

 34 (1867). 



Fort Gibson, Indian (Cherokee) Territory. 



Most nearly allied to Helix hazai'di, but readily distinguished 

 by the very different character of the parietal and basal teeth. 

 The species has no internal tubercle. 



Fig. 175. 



Helix troostiana, 

 enlarged. 



Helix troostiana, Lea.— Shell rimately um- 

 bilicated, discoidal, slightly convex above, flattened 

 below, obtusely carinated, with separated strong rib- 

 like strife throughout,' hirsute, russet horn-§olor ; spire 

 not much elevated ; whirls five and a half, flattened, 

 the last more convex, descending at the aperture, 

 grooved behind the peristome, with a smoother bulge, 

 below plane, widely rimated and ending in a small 

 umbilicus ; aperture oblique, subreniform, very much 

 contracted, far within on the base of the outer whirl 

 with a small, detached, erect, rounded tubercle ; peri- 

 stome white, thickened, continuous, ends approached, 

 joined by an excavated, emarginate, somewhat flexuose, 



' Some of the strise extend over the carina on to the base of the shell 

 without being carried into the umbilicus. 



