150 



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



Missouri, Tennessee, Mississippi, and Alabama. It is also found 

 in the postpleioeene beds of the Mississippi Valley. 



In H. clausa the umbilical region is more widely excavated, 

 and the groove, behind the reflected peristome, producing the 

 contraction of the aperture, is continued at the base of the shell, 

 becoming wider as it joins the umbilical opening. In H. mitch- 

 elliana the groove is almost obliterated at the point of reflection 

 of the peristome over the umbilicus, by the more tumid character 

 of the last whirl. 



Helix coSiimljiana, Lea. — Shell umbilicated, snbdepressed- 

 globose ; epidermis with short, rigid hairs, corneous, thin ; whirls sis, 

 slightly rounded, very minutely striated, rising gradually, but regularly, 

 one above the other to an acuminated apex ; suture 

 strongly impressed ; aperture roundly Innate, a little con- 

 tracted and thiekeiied, by a testaceous deposit or border, 

 at the angle of rellection of the peristome ; peristome 

 thickened, whitish, or bro« nish-w^hite, reflected but not 

 flattened, rather grooved on its face, the ba.«al margin 

 horizontal in its direction, with a slight thickening or 

 projection before it reaches the base of the shell ; um- 

 bilicus open, partially hidden by the rellec-ted peristome at its junetioa 

 with the base ; base a little flattened. Greater diam. 17, lesser 14 ; height 

 11 mill. 



Eelix Columbiana, Lea, Am. Phil. Soe. Trans. Vf, S.*), pi. xxiii, f. 75 ; 



Obs. II, 89 (1839) ; in Troschbl, Arch. f. Nat. 1839, II, 221.— 



DeKay, N. Y. Moll. 46 (1843).— Pfeiffek, Mon. Hel. Viv. I, 343; 



in Chemsitz, ed. 2, 1, 332, pi. Iviii, f. 10-12 (1846).— Reeve, Con. 



Icon. BO. 692 (1852).— Bisney, Terr. Moll. II, 169, pi. v.— W. G. 



Binxey, Terr. Moll. IV, 16. 

 Ilelix lahiosa, Gould, Proc. Bo.«t. Soe. Nat. Hist. IT, 165 (1846) ; U. S. 



Expl. Exped. Moll. 67, f. 35 (1852) ; Terr. Moll. II, 170, pi. xiii, a, 



f. 1. — Pfeiffek, Mon. Hel. Viv. I, 343. 

 Mesodon columbiana, Tkyon, Am. Journ. Conch. Ill, 46, pi. riii, f. 12-14 



(1867). 



A west coast species, from Sitka and Ft. Simpson (lat. 54^ 

 40') to Santa Cruz in California (lat. 37° 20') (Neivcomb). 



