XL. MOLLUSC A, IV: HELICIDAB. 



GENUS PLECTOPYLIS. 



By G. K. GuDE. 



(Plates xli, xlii). 



A small number of shells of the genus Plectopylis from the 

 Abor country has been kindly entrusted to me for examination. 

 They were collected for Lt.-Col. Godwin-Austen by Lieut. G. F. T. 

 Oakes, R.E., who accompanied the Abor Expedition as officer in 

 charge of the Survey Party, and all proved to be new to science. 

 Although the number of shells is small, they comprise no less 

 than seven species, two of them, unfortunately, being represented 

 by unique specimens. One species is of special interest owing to 

 the fact that it is a member of the section Sinicola, not previously 

 known to occur within the limits of the Indian region. 



Plectopylis, Benson (i860). 



Plectopylis (Endothyra) oakesi, sp. n. 



(PI. xli, figs. I, la, lb, ic, id). 



Shell sinistral, discoid, corneous, widely umbilicated, finely 

 and regularly ribbed, the ribs decussated by raised spiral lines. 

 Whorls 7, increasing slowly and regularly, the last not dilated 

 towards the mouth, slightly constricted behind the peristome, 

 shortly and rather suddenly deflexed in front, angulated above 

 and around the umbilicus, rounded at the periphery. Suture 

 linear, apex slightly raised. Aperture oblique, subrotundate ; 

 peristome shghtly thickened and reflexed, the margins united by 

 a slightly raised sinuous ridge, which has a slight notch at the 

 junctions with the peristome above and below. 



The parietal armature consists of a single strong, slightly 

 oblique transverse plate which gives off a short horizontal ridge 

 posteriorly above, the lower extremity is somewhat dilated and 

 notched, and gives off posteriorly a short ridge and anteriorly a 

 long thin fold, which runs parallel with and close to the lower 

 suture, joining the parietal ridge at the aperture. The palatal 

 armature is very complicated and consists of: 1°, a short slight 

 horizontal sinuous fold close to the upper suture; 2°, a short 

 stout transverse fold with posteriorly a slight denticle and ante- 

 riorly an elongated slender horizontal fold, raised in the middle; 

 3°, a stout transverse fold, concave posteriorly and giving off 



