136 HELIX-ISOMERIA. 



a narrow ridge connecting the ends of the peristome ; when there is 

 a tooth on the parietal wall it is small, compressed, and situated well 

 within the aperture. Large enough series have not yet been 

 examined to enable us to be certain of the constancy of several 

 characters upon which specific discriminations are founded, such as 

 the malleation of the last whorl, open or closed umbilicus, etc. The 

 teeth certainly vary in some forms, especially those which may be 

 developed on the upper border of the lip. 



H. OREAS Koch. PL 45, figs. 11, 12, 17, 18, 19. 



Umbilicate, depressed, solid, opaque, deep, rich chestnut brown ; 

 surface somewhat shining, obliquely striate, the stria? rather irregular, 

 distant, fold-like beneath the sutures, the base smoother ; all over 

 covered by a dense microscopic granulation ; scarcely, or not at all 

 malleated ; spire depressed ; apex very obtuse ; first two whorls quite 

 glossy, the following ones duller, more coarsely striate ; sutures 

 regularly and moderatelv impressed ; whorls 5, slightly convex, 

 regularly, not rapidly widening, the last transversely dilated, sub- 

 angular at the periphery and rather depressed and compressed on its 

 first two-thirds, the last third losing or nearly losing the angle, 

 tumid and convex beneath, deeply and suddenly deflexed anteriorly, 

 constricted behind the peristome, especially on the base ; aperture 

 very oblique, quadrangular, livid within, a trifle exceeding one-half 

 the diameter of shell ; peristome white, tinged with brown on the 

 outer-superior portion, reflexed all around, its face convex, the outer 

 portion bearing an acute compressed denticle near its junction with 

 the basal margin ; terminations joined across the parietal wall by a 

 narrow elevated white callous ; parietal wall bearing a small oblique 

 compressed white denticle ; columellar angle of the peristome 

 reflexed partly over the umbilicus; umbilicus rather narrow, deep, 

 scarcely narrowing as it penetrates, somewhat contracted by the first 

 half or two- thirds of the last whorl, then broadly expanding, with a 

 spiral sulcus inside, and generally rugose and obliquely striate 

 within. 



Alt. 26, diam. maj. 57, min. 46 mill. 



Alt. 23, diam. maj. 55, min. 44 mill. 



New Granada. 



Helix oreas KOCH in Philippi, Abbild. u. Beschreib. i, p. 151, 

 Helix t. 5, f. 2. PFEIFFER in Conchyl. Cab., p. 55, t. 75, f. 1-3 ; 

 Monographia i, p. 400. REEVE, Conch. Icon., f. 546. MOUSSON in 

 Malak. Bl. 1873, p. 2. DESHAYES in Fc'r., Histoire, t. 94, f. 1-4. 



