170 HELIX-LABYRINTHUS. 



This smallest species of Labyrinthus differs from others which 

 have a simple (not bifid) outer basal tooth, in being thinner, lighter 

 colored, with feebler teeth, the parietal one short, small, scarcely 

 joined to the elevated parietal peritreme edge. The superior lip- 

 tooth may be either present or absent, as in H. leucodon. The outer 

 basal tooth is marked behind the peristome by a small pit ; in the 

 larger, darker, flatter H. leucodon both basal teeth are so marked, 

 the outer much more conspicuously. 



*** 



2. S})ecies with the outer basal tooth bifid. 



H. TARAPOTONENsis Moricand. PI. 64, figs. 17, 18. 



Shell profoundly and broadly umbilicated, sub-lens-shaped, solid, 

 obliquely striate, minutely and irregularly granulate, chestnut- 

 colored ; spire obtuse ; suture impressed ; whorls 5, nearly flat, the 

 last obtusely carinated, deflexed anteriorly ; aperture very oblique, 

 ear-shaped ; peristome continuous, white, subthickened, parietal 

 margin an erect lamina, right margin rounded, basal margin sub- 

 angularly descending in the middle, the right side with two teeth, 

 one simple, acute, the other bifid, white. (Moric.) 



Alt. 12, diam. maj. 34, min. 28 mill. 



Tarapoto, Andes of Peru. 



H. tarapotonensis MORIC. Rev. et Mag. de Zool. 1858, p. 450, t. 

 13, f. 2. PFEIFFER, Monographia Hel. Viv., v, p. 411. 



This species belongs to the group of H. bifurcata; it resembles H. 

 furcillata Hupe, but the constantly very different position and form 

 of the teeth and lamella, and the very different granulation dis- 

 tinguishes it. In the furcillata the two teeth are far apart, but 

 supported by a common base ; in this species one tooth is simple and 

 conical, nearer the umbilicus than the other extremity of the 

 aperture ; the second is double, its base not at all elongated. 

 (3/oric.) 



H. BIFURCATA Deshayes. PI. 64, figs. 22, 23, 24, 25. 



The original figures given by Deshayes are copied on plate 64,. 

 figs. 22, 23. Those of Ferussac, to which Deshayes refers are on 

 plate 42, figs. 29, 30, 31 ; and these last differ from the others in 

 having the parietal entering lamina joined to the callous connecting 

 the ends of the peristome. Pfeiffer's description is as follows : 



