158 HELIX-ISOMERIA. 



H. AEXIGMA Dohrn. PL 39, figs. 93, 94 ; pi. 44, figs. 1, 2. 



Umbilicate, depressed-subgiobose, solid, striate, the striation rather 

 coarse just beneath the sutures, fine on base, the whole surface 

 microscopically very densely, regularly granulated ; shining, chestnut 

 brown ; spire convex, sutures scarcely impressed ; whorls 4^ to 5, a 

 little convex, slowly increasing, the last more rapidly widening, 

 carinated at the periphery, transversely dilated, very convex beneath, 

 especially on its last third, where it is less carinated at periphery 

 and much swollen below, deflexed anteriorly, constricted and biscro- 

 biculate behind the peristome ; aperture ear-shaped, very oblique, 

 purplish-white inside ; peristome light brown, continued as an 

 elevated callous plate across the parietal wall ; upper and outer 

 margins of peristome broadly expanded, arcuate, the outer bearing 

 a fold-like tooth just above the place of termination of the periphery, 

 and a strong entering fold extending to the edge of peristome, and 

 marked behind the lip by a pit or scrobiculation ; basal lip sinuous, 

 reflexed, in the middle bent upward, forming an obtuse squarish 

 process narrowing the aperture ; parietal callous continued in an 

 elevated erect fold entering the aperture ; umbilicus rather narrow, 

 partly closed by the inflated last whorl and the inner expansion of 

 the columellar lip. 



Alt. 23-25, diam. maj. 45-48, min. 38-39 mill. 



Andes of Colombia at Frontino, 2000 meters alt. 



H. cenigma DOHRN, Nachrichtsbl. d. Malak. Gesell., 1875, vii, p. 

 56; Jahrbiicher d. Malak. Gesell., ii, 1875, p. 292, t. 10, f. 1, 2 ; 

 Continuation of Conchylien Cabinet, p. 625, 1. 180, f. 1,2. PFE. Mon- 

 ographia, vii, p. 591. 



H. VEXANS Dohrn. PL 44, figs. 5, 6 ; pi. 42, figs. 38, 39. 



Umbilicate, depressed, solid, striate, shining, angulate, chestnut- 

 brown ; spire subcouvex ; whorls 4=}, nearly plane, the last angulated, 

 convex beneath, suddenly deflexed at the aperture, coarctate, and 

 bi-scrobiculate on the base ; aperture nearly horizontal, rhombic- 

 auriform, ringent ; peristome expanded, parietal margin angularly 

 bent in at the middle, and giving rise to a long entering plate or 

 fold ; right margin bi-tuberculate ; basal rnafgin incurved in the 

 middle and bidentate ; columellar margin extending partly over the 

 umbilicus. (Dohrn.} 



Alt. 12, diam. maj. 28, min. 24 mill. , 



Canas Gordas, Colombia. 



