SYSTENOSTOMA. 225 



circular, oblique and toothless; peristome thin, free or very 

 shortly adiiate, expanding very little. 



Type: S. pauperrima. 



Distribution: Tonkin, Indo-China. 



Figured on plate 38. This genus was at first thought to be 

 Helicid. Subsequently Messrs. Bavay and Dautzenberg 

 wrote: "A close examination of the four 1 forms leads us to 

 think now that the genus Systenostoma, which we placed 

 among the Helices, belongs to the Pupse, and is to be put in 

 the neighborhood of Hypselostoma and Boysidia; the Systeno- 

 stoinas being, if we may so express it, toothless Boysidias. 

 These rnollusks live 011 rocks, probably subsisting upon the 

 lichens with which they are draped. ' ' 



My knowledge of Systenostoma is wholly from the writings 

 of Bavay and Dautzenberg, translated below, from which I 

 get the impression that it is closely related to Aulacospira. 

 It differs by having the whorls rounded instead of keeled, 

 and the lip less expanded, almost simple. 



1. SYSTENOSTOMA PULVEREA (Bav. et Dautz.). PI. 38, figs. 10, 

 11, 12. 



The shell is very small, thin, umbilicate; spire conoid. 

 Whorls 4:^/2, convex, terraced, rapidly increasing, ornamented 

 with delicate, oblique lines of growth, and very delicate spiral 

 lines, only visible under a very strong lens, The last whorl is 

 carried towards the axis. Umbilicus moderate. The aperture 

 is oblique, subrotund; peristome simple, very slightly thick- 

 ened, free almost throughout, but dilated and adnate 011 the 

 penult whorl, a little reflected at the umbilicus. Color dull 

 pale gray, dirty with agglutinated dust. Alt, 2.5, diam. maj. 

 2.5, diam. aperture 1.5 mm. (B. et D.). 



Tonkin: Phu-Quoc-Oai, on rocks (M. Demange). 



Helix (Systenostoma) pulverea BAVAY et DAUTZENBERG, 

 Journ. de Conchyl., Ivi, 1909, p. 243 ; Ivii, p. 194, pi. 8, f. 7-9. 



2. SYSTENOSTOMA PAUPERRIMA (Bav. et Dautz.). PI. 38, figs. 

 3, 4, 5. 



The shell is very small, conoid, apiculate (the embryonic 11/2 

 whorls forming a nearly cylindric apex), umbilicate. Five 



