76 GASTROCOPTA, NORTH AMERICA, WEST INDIES. 



Cab., p. 138, pi. 17, figs. 27, 28. Vertigo pellucidus Pfr., 

 ARANGO, Fauna Malac. Cubana, p. 103 (in part). Pupa hor- 

 deacella PILSBRY, Proc. A. N. S. Phila., 1890, p. 44, pi. 1, f. g, 

 h, i, j, k. Bifidaria hordeacella PILS. & VAN., Proc. A. N. S. 

 Phila., 1900, p. 594, pi. 22, f. 3. VANATTA, Nautilus, xxvi, 

 1912, p. 17, pi. 2, f. 1-27 (variation). WALKER, Occ. Papers 

 Mus. Zool. Univ. Mich., no. 15, 1915, pp. 2-11 (distribution). 



G. pellucida is cylindric-oblong, diameter almost equal at 

 the last two whorls, those above tapering convexly to an ob- 

 tuse apex. The color is "corneous" that is, an imperfectly 

 transparent, very pale grayish-buff, but on red soils the thin 

 cuticle becomes stained, slightly cinnamon in some cases. The 

 striation is well developed. The last whorl is strongly flat- 

 tened over the lower palatal plica, and has no trace of a crest 

 or ridge behind the lip. Peristome expanded, very slightly 

 thickened within, corneous, the terminations remote. The an- 

 gulo-parietal lamella is not very conspicuously bifid in front 

 view. Seen from below (pi. 15, fig. 5) it consists of a straight, 

 grayish angular lamella highest at its junction with the pari- 

 etal, and a thicker, more opaque whitish parietal lamella, the 

 front end of which curves slightly towards the columella, 

 forming a minute projection on that side a little forward of 

 the middle of the whole lamella. The columellar lamella is 

 stout, horizontal, and has a small callous below its inner end, 

 often not visible in a front view. The lower palatal plica is 

 larger than the upper, and is placed a little deeper. Basal 

 fold short but distinct. As in other Bifidarias, there are some- 

 times abnormalities in the palatal region, plicae being doubled, 

 or irregular ones interposed. 



Length 1.75, diam. 0.8 mm. ; 5 whorls. 



Length 1.7, diam. 0.75 mm. ; nearly 5 whorls. 



G. pellucida has been used to cover almost any species of 

 its group, as I gather from the literature and the named 

 specimens in various museums. The original account and 

 Kuester's figures are not very satisfactory. The above de- 

 scription and pi. 15, figs. 1-3, 5, are from typical Cuban 

 specimens. Its recognition marks are the small size (1.5 to 

 2.2 mm. long), faintly yellowish-corneous tint, rather indis- 



