HELIX-LABYRINTii^i^ORNlA.^/ 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}, 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 



HP. 



Alt. 8, diam. maj. 17}, min. 16} mill. 

 Alt. U-T, diam. maj. 24, min. 22 mill. 



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 Pfeifler's types (the 

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

 long to " var. ,3. minor, fusco-cornea, umbilico paullo angustiore." 



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



Narrowly, half covered uinbilicate, 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 plicae joined at their bases. (Pfr.) 



Alt. 9, diam. maj. 20, min. 17} mill. 



Santa Fe de Bogota. 



