GYLIAUCHEN. 215 



straight or even descends a little in front, and the aperture is 

 a little oblique, the upper margin of the peristome advancing 

 further than the lower, in this respect differing from the re- 

 lated species, which look upward. In the somewhat similar 

 G. crossei the lower margin is advanced, as usual. 



The surface is closely sculptured with short wrinkles, or 

 they might be called long, irregular, coarse granules. The 

 first whorl is distinctly granulous. This sculpture is only 

 visible under the compound microscope. The original figures 

 are reproduced in figs. 6 and 7. 



The Samui Islands, in the Gulf of Siam, are a small group 

 south of Bangkok and situated near the coast of the Malay 

 Peninsula at its narrowest part. It consists of several small 

 islands, the largest of which is called Samui. The rock seems 

 to be calcareous throughout. 



4. GYLIAUCHEN STRIOLATUS (Moellendorff). 



Owing to the bad state of preservation of the two speci- 

 mens of this form, quite distinct from the preceding one, I 

 cannot give a complete description of it. Its last whorl is 

 much more detached than in H. transitans and distinctly bent 

 upwards, and shows very distinct though minute spiral lines. 

 The diameter is only 2.5 millim. It belongs to the group of 

 H. bensonianum and H. hungerfordianum (Mdllff.). 



Hypselostoma striolatum MLLDFF., Proc. Zool. Soc. Lond., 

 1894, p. 152. 



Samui Is. (Roebelen). 



5. GYLIAUCHEN CROSSEI (Morlet). PL 36, figs. 9-13. 



Shell perforate, conic, of irregular form, small, thin, brown, 

 sometimes lineolate with white, radially, delicately striate. 

 Spire acute; whorls 5, rapidly increasing, separated by a 

 channelled suture, the first smooth, prominent, papillar; the 

 last partly free, carinate in the middle, channelled below and 

 around the umbilicus, subtrigonal, at the end forming a tube. 

 Aperture subtrigonal or subquadrangular, reflexed, brownish, 

 somewhat channelled above, denticulate deep within, the teeth 

 numerous, acute, unequal (4 or 5 larger ones). Umbilicus 

 narrow, deep, angulate at the periphery. Peristome thin, a 



