VALLONIA. 255 



rapidly expanding to the aperture, descending only at the suture in 

 front. Aperture very oblique, tangental, and rather inclined, 

 almost circular, with ends of margins somewhat protracted ; peristome 

 straight above,. abruptly everted below, with a strong, whitish lip. 



Alt. 0-8, greater diam. 2*0, lesser 1-6 mill. 



Central part of North America; Illinois, Iowa, Nebraska, Kansas, 

 Indian Territory. 



This species closely resembles in shape V. costata, with which it is 

 found, but it is constantly much smaller, having only half the bulk 

 of the latter, and differs also in the wider umbilicus, the flat spire, 

 the last whorl not being decurved at all on its back, but quite 

 straight to the margin, or quite commonly ascending (like some 

 specimens of V. excentrica, fig. 6, pi. 32) ; the ribs stand more 

 densely, as a rule, than in V. costata. It resembles also V. perspec- 

 tiva, q. v. 



V. TENERA Reinhard. PI. 43, figs. 64, 65, 66. 



Bather widely and regularly umbilicated, with little elevated spire, 

 the apex prominent. Light grayish horn colored, translucent ; with 

 with fine and dense membranous ribs. Whorls rather more than 

 3 2, regularly increasing, a little angular at the periphery, with a 

 deep suture, the last moderately wide, distinctly flattened above and 

 sloping outward, somewhat expanding toward the aperture, ascend- 

 ing and then moderately descending in front, a little more so at the 

 suture. Aperture very oblique and inclined, transversely elongated, 

 markedly flattened above, moderately curved below, margins much 

 approximating, the superior more advancing in front; peristome, 

 except above, moderately and abruptly everted, with a rather thin, 

 almost glassy transparent lip. 



Alt. !, greater diam. 2*3, lesser 1*9 mill. 



China (Shanghai) and Japan (Kobi, Nippon.) 



Hel. tenera REINHARD, Jahrb. D. Mai. Ges. 1877, p. 322, t. xi, 

 fig. 4. 



General aspect of costata, but the last whorl and aperture dis- 

 tinctly flattened above. The dense fine ribs (38-43 on the last 

 whorl), the grayish tint, distinguish it sufficiently from that species 

 and from F. parvula. 



F. pulchellula Heude (Helix pulchellula Hde., Notes sur les 

 Moll. Terr. Vallee Fl. Bleu, p. 20, t. 13, f. 17) is not superficially 

 distinct from tenera. Among two different and evidently authentic 



