HELIX-LAB YRINTHUS. 173 



May be known by the depressed, flattened form, acute periphery 

 and diverging branches of the outer basal tooth. 



H. YATESI Pfeiffer. PL 42, figs 34-37. 



Umbilicate, depressed, acutely carinated, thin, chestnut-colored ; 

 surface delicately striate, under a lens very minutely granulated all 

 over ; spire low-conoidal, apex blunt, suture scarcely impressed ; 

 whorls 4 J, almost flat, the outer ones wide, last whorl acutely keeled 

 at periphery, tumid on the base around the umbilicus, very deeply 

 abruptly deflexed anteriorly, deeply constricted and bi-scrobiculate 

 behind the basal lip ; aperture nearly horizontal, transverse ; per- 

 istome white, expanded, continuous, thin, basal margin reflexed, 

 sinuous, with two teeth, the outer with two acute diverging branches, 

 the inner a small, narrow, blunt fold ; parietal elevated plate 

 connecting the terminations of peristome straight ; not connected 

 with the obliquely entering parietal plate-like tooth. Umbilicus 

 variable in width, partly closed by the reflection of the columellar 

 lip. 



Alt. 8, diam. maj. 17J, miu. 16? mill. 



Alt. 9i, diam. maj. 24, min. 22 mill. 



J V 



Solimoes River, Brazil. 



H. yatesi PFEIFFER, Proc. Zool. Soc. Lond. 1855, p. 92, t. 31, f. 

 13, 14; Monographia Hel. Viv., iv, p. 306. 



The specimens before me are all smaller than Pfeiffer's types (the 

 measurements last given above are from Pfr.). They probably be- 

 long to " var. /9. minor, fusco-cornea, umbilico paullo angustiore." 



H. ELLIPSOSTOMA Pfeiffer. PI. 41, fig. 22. 



Narrowly, half covered umbilicate, conoidal, thin, striate and 

 under a lens very minutely granulate, brown ; spire conoidal, sub- 

 acuminate ; suture linear, submarginate ; whorls 5, nearly flat, 

 visibly widening, the last acutely carinated, abruptly deflexed ante- 

 riorly ; base somewhat convex, tri-scrobiculate behind the lip ; aper- 

 ture almost horizontal, elliptical-rhomboidal, with a free lamelliform 

 entering tooth ; peristome continuous, white, the parietal margin 

 erect, upper margin narrowly expanded, basal margin reflexed, sub- 

 angularly descending in the middle, the left side with a single tuber- 

 cle, right side with two diverging plica? joined at their bases. (Pfr.) 



Alt. 9, diam. maj. 20, min. 17-j mill. 



Santa Ft de Bogota. 



