HELIX-LABYRINTHUS. 171 



Shell umbilicate, sub-lens-shaped, solid, arcuately stria te and 

 appearing very minutely granulate under a lens, deep chestmit color, 

 more or less acutely carinated, and encircled with whitish at the 

 carina ; spire short, convex, obtuse ; suture lightly impressed ; whorls 

 5, scarcely convex, the last abruptly deflexed anteriorly; base 

 deeply scrobiculate ; aperture very oblique, transversely pyriforrn, 

 divided by an elongated, free, compressed parietal lamina ; peristome 

 white (rarely liver-brown), continuous, the parietal margin erect, 

 partly uncovering the umbilicus, right margin expanded, basal mar- 

 gin sinuous, the left side bearing a subtransverse tooth, right side 

 with two diverging teeth, joined at their bases. 

 Alt. 14, diam. maj. 36, min 30 mill. (Pfei/er.') 

 Alt. 12, diam. maj. 38, min. 34 mill. (Pfeiffer.} 

 Alt. 10, diam. maj. 21 i, min. 18 mill. (Pfei/er. ) 

 H. bifurcata DESK., in Guerin's Mag. de Zool., 1838, t. Ill, f. 2. 

 PFEIFFER, in Bolster's Conchyl. Cab., p. 207, 1. 105, f. 1-4; Monog. 

 Hel. Viv., iii, p. 255 ; iv, p. 305 ; v, p. 411. REEVE, Conch. Icon., 

 f. 554. MARTENS, Binnenmoll Venez., p. 72. H. plicata FEE., 

 Histoire, t. 54B, f. 1. DESK., Encyc.Meth., ii, p. 231. (Excl. synon.) 



This seems to be a very variable species, and I am unable to point 

 out the characters separating it from H. raimondii and H. fur- 

 cillala. It is sometimes small and only obtusely carinated at the 

 periphery ; and the umbilicus is sometimes wholly closed by the ex- 

 panded columellar lip. 



H. bifurcata, tarapotonensis, furcillata and raimondii form a group 

 of very closely allied forms, the exact rank, affinities and distinctions 

 of which remain to be ascertained when more numerous specimens 

 are collected and compared. It is at present extremely difficult to 

 separate by any good characters the first three. I doubt whether 

 those drawn from the outer basal tooth are constant. 



H. FURCILLATA Hupe. PI. 39, figs. 91, 92. 



Umbilicate, sub4ens-shaped, solid, obliquely striate, under a lens 

 punctate-granulate, chestnut-colored ; spire short, obtuse ; suture 

 lightly impressed ; whorls 5, scarcely convex, the .last more convex, 

 obtusely carinated, deflexed anteriorly, broadly bi-scrobiculate on 

 the base ; umbilicus moderate, deep ; aperture very oblique, trans- 

 verse pyriform, the parietal wall traversed by a compressed, free 

 callous plate ; peristome continuous, white, sub-thickened, parietal 

 margin erect, partly concealing the umbilicus, right margin rounded, 



