227 



ON THREE SPECIES OF DYAKIA FROM WESTERN SUMATRA. 



By E. R. Sykes, B.A. 



Read \Zth January, 1905. 



The shells now discussed form part of an interesting collection wMcli 

 has recently been sent to me for determination. 



Dtakia geanaria (Bock). 



Helix {Nanina) granaria, Bock: Proc. Zool. Soc, 1881, p. 628, 

 pi. Ixv, fig. 1. 



This species was described by Bock from a single specimen, which 

 is now in the British Museum. My specimen is a trifle larger (46 mm. 

 in diameter, the type being 40 mm.), and slightly more depressed in 

 form, thus giving the aperture the appearance of being more drawn 

 out to one side. The sculpture is similar to that of Bock's specimen, 

 including the striking elevated ridge on the last whorl, but entirelj^ 

 lacks the wrinkling or malleation to which he refers and which is 

 very conspicuous on the last whorl of the type. 



Dyakia peesteiata, n.sp. Fig. 2. 



Shell sinistral, depressed trochiform, narrowly but deeply umbili- 

 cated, somewhat thin, brown horn colour, being paler above and also 



Fig. 1. 



Fig. 2. 



near the umbilicus ; the protoconch is almost smooth, then subgranulose 

 wrinkling appears, becoming from the third whorl onwards well 

 marked radiating rib- striae, these rib-striae are cut on the third whorl 

 by spirals, which gradually become less conspicuous, until the last 

 whorls appear only to bear strong rib-striae, which are subgranular ; 

 below, the shell is lightly marked by irregular wrinkled lines of 

 growth, with, under a lens, indications of closely-set spirals ; whorls 6^, 

 flattened, slowly but regularly increasing ; suture not much impressed ; 



