1893.] NATURAL SCIENCES OF PHILADELPHIA. 273 



enabled to identify it, and now would add the following: Shell 

 rather thin, pale or grayish-horn colored, or whitish translucent, 

 ribs on the shell small, crowded (about 60 on the last whorl), with 

 fine membranes, rather regular, often irregular (as in Man. Couch., 

 PI. 32, fig. 29), with fine stria? between them ; nucleus with slight, 

 irregular, nearly obsolete revolving lines ; suture moderately deep ; 

 last whorl somewhat widening toward the aperture, in its last i dis- 

 tinctly ascending (Man. Conch., PL 33, fig. 37) then rather rapidly 

 descending, somewhat more at the suture, so that the margins are 

 much approximate; aperture transversely elongate ; superior mar- 

 gin markedly less curved than inferior ; peristome slightly everted, 

 except near the suture, thin, without a lip. Most specimens are of 

 a rather dull surface, but those from Walla Walla are shining, the 

 shell almost colorless, thin and transparent, and rather large. 



Greater diam. 2 - 7, lesser 2*2 alt. 1*2 mm. 



I have seen no living animals. The jaw and radula were exam- 

 ined in softened specimens. The former appears rather low, some- 

 what truncated at the ends, with rather stout, irregular rib-stria?, 

 except near the side-ends, which are smooth. The radula (PI. VIII, 

 f. E) has 63 transverse rows of 25 teeth ; 5 laterals, the fifth though, 

 having' a small plate; its ectodont is simple in most, slightly two- 

 pointed in a few teeth. The first marginal (sixth tooth) is some- 

 what different from the following : the plate is distinctly visible 

 behind the "reflection," the latter markedly tapering from the 

 proximal end ; the mesodont comparatively large, the others 2-3, 

 small. In the following marginals the cusps are comparatively 

 small, about 6, the mesodont little exceeding the others, and only in 

 the 2-3 -first teeth ; the last ones are very short aud with very small 

 cusps. 



There is some variation in the configuration of the shell as has 

 already been pointed out. Some specimens from Hamilton, Nevada, 

 in the Nat. Mus. Coll., have a distinct though not strong lip. 



13. V. tenuilabris, A. Braun. 



Hel. tenuilabris, Vers. D. Naturf., Main, 1843, p. 143. 



Hel. tenuilabris Sandberger, Conch, d. Vorw. p. 891, T. 36, f. 14. 



Hel. tenuilabris Westerlund, Fauna, I, p. 15. 



" Shell with umbilicus open, and rapidly widening at the aper- 

 ture, depressed convex, with prominent, almost papilliform apex, 

 with fine and acute, crowded ribs, grayish horn-colored ; whorls 4- 

 4J, somewhat convex, the last somewhat expanding in front, grad- 



