38 



PROCEEDINGS OF THE ACADEMY OF 



[March, 



This species of the section Sinica is smaller than D. paxillus Gredler, 

 and differs by its smooth last whorl and very short palatal plica. It 

 is more related to D. hungerfordiana of Formosa, which differs in 

 shape. D. schmackeri Mlldff. is unlike hangchowensis by the shape of 

 the aperture. 



A variety also from Hangchow may be called D. hangchowensis 

 granum. It is larger, length 2.7, diam. 1.5 mm., with 6 whorls and 

 pale reddish-corneous color. The cone of the spire is longer than in 

 D. hangchowensis. 



HYDROOBNID^. 



The genus Georissa is represented by six species in China : G. hach- 

 manni Gredl., G. sinensis Hde., G. nivea Hde., G. sulcata Mlldff., 

 hungerfordiana Mlldff., and G. heudei P. & H. In all of these except 

 sinensis and heudei the glossy, flat operculum is retracted some dis- 

 tance in the aperture. This is the normal condition in Georissa. 



In G. sinensis and G. heudei the thick, calcareous operculum lodges at 

 the edge of the peristome, as in Bithynia, being larger than in Georissa 

 proper. We propose to signalize this feature by the erection of a new 

 subgenus Georissopsis, the type being G. heudei. 

 Georissa (Georissopsis) heudei n. sp. Fig. 2. 



The shell is minutely perforate or subperf orate, conic, higher than 

 wide, gray, more or less reddish in places, sculptured with very fine, 



close spiral striae, usually in 

 large part lost by erosion. 

 There are 3^ to 3f whorls, the 

 first corneous and glossy, the 

 rest very convex, separated by 

 deep sutures. The aperture is 

 subvertical, broadly semicir- 

 cular, the outer margin very 

 convex, inner margin nearly 

 straight; the basal margin is 

 very broadly rounded, the 

 upper end narrowly rounded. 

 The peristome is thin, acute; 

 the inner lip is built forward, 

 standing free from the whorl except for a short space near the posterior 

 end, leaving an umbilical area. 

 Length 3.4, diam. 2.1 mm. 

 The operculum lodges at the lip-edge. It is between triangular and 



Fig. 



2. — G. heudei and outline of oper- 

 culum, interior view. 



