154 HELIX-ISOMERIA. 



are with open umbilicus, the others having it closed by a thick 

 deposit. The dimensions vary between 



a. diam. maj. 29, min. 25, alt. 15 mill., and 



b. diam. maj. 24, min. 20, alt. 12 mill. 

 Miller's H. loxensis is figured on pi. 64, fig. 26. 



H. BASIDENS Mousson. PL 48, figs. 52-54. 



Imperforate, very depressed globose, rather solid, transversely 

 striate, especially at the suture, under a lens very minutely granulate, 

 blackish brown. Spire convexo-depressed, regular; apex not 

 prominent ; suture lightly impressed, simple ; whorls 4?, moderately 

 increasing, the upper ones planulate, carinated, the last angulated, 

 the angle becoming evanescent, anteriorly briefly descending, sub- 

 inflated and constricted, broadly inflated beneath. Aperture oblique, 

 transversely semioval, grayish-brown inside ; peristome reflexed, 

 margins subparallel, not converging, joined by a callous plate, 

 upper and outer margins regularly curved, basal margin thickened, 

 with a somewhat fold-like nodule or tooth and a callous thickening 

 toward the columella ; columellar margin short, broadly reflexed 

 and adnate. (Mousson.) 



Alt. 14, diam. maj. 24, min. 21 mill. 



Bogota. 



H. basidens Moussox in Malak. Blatter 1873, p. 2. PFEIFFER, 

 Novit. Conch., iv, p. 118, t. 127, f. 7-9 ; Monographia, vii, p. 362. 



This species stands nearest to H. bituberculata Pfr., but is separated 

 from that species by numerous characters. It is somewhat larger, is 

 more depressed, the apex not so prominent ; it is imperforate, and 

 the whorls are flatter, keeled in the young, finally becoming bluntly 

 angled ; on account of the scarcely widened upper margin, the 

 aperture is narrow 7 , and has a single, not very conspicuous tooth or 

 node on the basal lip, a callous thickening beginning there, and 

 continuing to the columella. Finally, the short coluniellar-margin 

 is broadly reflected and wholly appressed. In these characters it 

 stands between H. bituberculata and jET. neoyranadensis. (Pfr.) 



H. BITUBERCULATA Pfeiffer. PI. 47, figs. 36, 37, 38. 



Umbilicated, depressed-globose, thin but strong, chestnut-colored 

 or dark chestnut reddish ; surface shining, lightly obliquely striate 

 and obsoletely very minutely granulated ; spire low, convex, apex 

 obtuse, planulate ; sutures moderately impressed ; whorls 4, a little 

 convex, slow r ly widening, the last wider, somewhat oblong or trans- 



