214 GYLIAUCHEN. 



Specimens from the limestone caves of Gunong Pondok (pi. 

 36, fig. 1) have the scaly-granose sculpture strongly developed 

 and the keel more pronounced. The figured specimen meas- 

 ures, alt. 2, diain. 3 mm. Figures 2-4 are Perak specimens, 

 probably of the original lot. 



3. GYLIAUCHEN TRANSITANS (Moellendorff). PL 36, figs. 5-8. 



Shell urnbilicate, turbinate, obliquely striatulate, brown. 

 Whorls 4, convex, forming a conic spire with papillar apex ; 

 the last whorl a little distorted, not ascending in front, shortly 

 free and produced forward, at the periphery encircled with a 

 rather prominent crest, another smaller one at the umbilicus ; 

 the base somewhat swollen, compressed around the umbilicus. 

 Aperture slightly oblique, rounded-tetragonal ; peristome con- 

 inuous, thin, expanded, hardly reflected. Parietal lamella 

 rather strong, bifid in front; two teeth in the outer margin, 

 one in the base and one on the columella. Diam. 2.75, alt. 

 2.66mm. (Mlldff.). 



Samui Is. (C. Roebelen). 



Hypselostoma transitans MLLDFF., Proc. Zool. Soc., 1894, p. 

 16, f. 12, 13. 



' ' This peculiar shell presents an especial interest, inasmuch 

 as it forms a decided transition from Hypselostoma to the In- 

 dian and Chinese Boysidia Ancey, of which Pupa hunanensis 

 Gredl. is the type. As I. have mentioned in the description of 

 Hypselostoma hungerfordianum (P. Z. S., 1891, p. 338) the 

 genus appears to be but an extreme development of the Boy- 

 sidia type. Boysidia. stropkostoma Mldff. of South China 

 shows already a slight distortion and detachment of the last 

 whorl, which in the Samui species is much less developed than 

 in the other forms of the genus. There can be no doubt, how- 

 ever, that it belongs to Hypselostoma, with which it has the 

 peculiar quadrangular shape of the last whorl and the denti- 

 tion of the aperture in common. H. crossci Mor. of Tongkin 

 seems to connect it with the other Malayan species" (Mlldff.). 



The angular lamella is quite short and parallel to the pari- 

 etal, but distinct from it (fig. 5) ; the two palatal plicas are 

 about equal, the basal plica much smaller. The last whorl is 



