HELIX-LABYRINTHUS. 175 



nut band ; surface shining, very delicately striate, under a lens seen 

 to be granulate (more densely than in H. yatesi, leprieuri, etc.) ; 

 spire very low, nearly flat, apical two whorls whitish, free from gran- 

 ulation ; whorls 44, nearly flat, the last wide, but becoming narrower 

 behind the aperture, very acutely carinated at the periphery, very 

 deeply, abruptly deflexed in front, constricted and bi-scrobiculate 

 behind the basal lip ; aperture nearly horizontal, oval ; peristonie 

 continuous, thin, expanded ; parietal wall bearing a slightly sinuous 

 obliquely entering lamellar tooth ; basal lip with a bifid outer tooth, 

 a rather deep rounded central sinus, followed by a narrow fold ; 

 between this and the columella there is an elongated fold or tooth, 

 parallel with the lip. All of the teeth are rather deep-seated. 

 Umbilicus broad. 



Alt. 8, diam. maj. 19, min. 18 mill. 



Alt. 7z, diam. maj. 22, min. 19 mill. 



Andes of Colombia. 



H. dunkeri PFEIFFER, Proc, Zool. Soc. 1852, p. 157 ; Mono- 

 graphia Hel. Viv., iii, p. 256. REEVE, Conch. Icon., f. 559. PFR. 

 in Conchyl. Cab., p. 365, t. 138, f. 21-23. 



May be known by the greatly deflexed aperture, very acute 

 periphery, and four teeth of the basal margin, caused by the splitting 

 of the two normal teeth. 



H. ISODON Pfeiffer. PI. 64, fig. 19-21. 



Narrowly umbilicated, conoid-lenticular, solid, all over minutely 

 granulated, chestnut-brown ; spire broad-conoidal, obtuse ; whorls 5, 

 scarcely convex, slowly widening, the last carinated, very deeply 

 deflexed in front, constricted and scrobiculated ; base convex ; aper- 

 ture nearly horizontal, ear-shaped; peristome brownish, somewhat 

 thickened, reflexed, margins joined by an elevated flexuous callous, 

 which gives rise in the middle to an entering tongue-shaped lamina; 

 right margin much curved, bidentate, basal margin sloping, uniden- 

 tate ; teeth subequal, strong, a fourth obsolete one on the columella. 

 (Pfeiffer.) 



Alt. 10t, diam. maj. 19, min. 17* mill. 



Western Colombia. 



H. isodon PFR., Proc. Zool. Soc. Lond. 1852, p. 84 ; Couchyl. 

 Cab., p. 490, t. 160, f. 19-21 ; Monographia, iii, p. 257. REEVE, f. 

 965. 



Allied to H. dunkeri, but unicolored, more elevated, etc. 



