26 



GASTROCOPTA, NORTH AMERICA, WEST INDIES. 



holzingeri var. fordiana STERKI, Nautilus, vi, 1892, p. 4 (nude 

 name). Bifidaria agna PILSBRY and VANATTA, Nautilus, xx, 

 1907, p. 140, figs. 1-3. 



G. Iwlzingeri differs from G. contracta by its nearly cylin- 

 dric shape, the presence of a strong basal fold, the small size, 

 and discontinuous peristome. The columellar lamella (fig. 6) 

 ascends the axis and towards the upper end curves forward 

 almost exactly as in G. contracta. It differs from both con- 

 tracta and armifera by the shape of the angulo-parietal 

 lamella, which is forked in front, and in a basal view has the 

 shape of the Greek letter A, as in the subgenus Immersidens 

 (pi. 2, fig. 4). The palatal callous and armature, however, 

 are typical for Albinula. 



It is not an uncommon species in Illinois and Iowa; found 

 also in Minnesota (Wiiiona), Dakota, Nebraska, etc. 



3a. G. holzingeri agna Pilsbry & Vanatta. PI. 2, fig. 7. 



The shell is rimate, cylindric, the last three whorls of about 

 equal diameter, the summit very obtuse; surface nearly 



Figs. 9-11. Gastrocopta holzingeri agna. 



smooth; of a spermaceti- whitish color. There are 4% convex 

 whorls, the last with a strong rounded crest behind the outer 

 lip, rather close to it above, but being more oblique, it is fur- 

 ther behind the lip at the base. Behind the crest the whorl 

 is a little flattened laterally, and shows the lower palatal plica 

 through as a white spot. The aperture is brought forward 

 nearly in line with the ventral convexity of the whorls. The 



