THE MOLLUSCA OF COLORADO QI 



right-hand angle of aperture, i above it, sometimes i or 2 others, peri- 

 stome broadly reflected, height 4 to 4 . 5 mm., width 2 . 25 mm. 



Bifidaria armifera 



gg. Whitish, very small, outline as in armifera, whoris 5, 8 teeth, i on columella, 

 3 on base, 3 on inner side of lip, a long one extending dow^nward from 

 parietal wall, peristome slightly reflected, height 2 mm., width about i mm. 



Bifidaria pentodon 



hh. Chestnut brown, perforate, middle 3 whorls about equal, last expanding 

 toward base, with tendency to separate from penultimate one, peristome 

 simple, slightly reflected over umbilicus. Sphyraditim edentulum 



2. Whorls 5 or less. 



aa. Color dark amber, ovate, whorls 5, increasing somewhat regularly and 

 rapidly, last inflated, peristome somewhat expanded, with groove behind 

 and thickened within, umbilicus expanded, 2 parietal teeth, i columellar, 

 2 basal, I inside outer margin of aperture, height 3 mm., width i . 5 mm. 



Vertigo ovata 



bb. Amber-colored, narrowly ovate, highly polished, whorls 5, one tooth on 

 middle of lower hp, and one on parietal wall, one on columella and a small 

 one within outer lip. Vertigo tridentata 



cc. Color light chestnut, cylindrical ovate, whorls 4 or 4J, increasing slightly 

 after the second, last about \ length of shell, umbilicus slightly open, teeth 

 variable, i to 3 parietal, i columellar, i at lower left-hand angle, 2 on 

 oblique base and outer lip, sometimes i above and i below latter two, 

 peristome thickened but not reflected, width i mm. Vertigo gouldi 



dd. Ovate to oblong ovate, whorls 4, smooth, polished, one parietal tooth, 2 

 columellar and 2 basal, outer margin of aperture fleunose, peristome 

 reflected. Vertigo ventricosa elatior 



ee. Shape as in gouldi, but last 2 of the 3I whorls equal, umbilicus distinct, lip 

 reflected, i parietal tooth, i columellar, 2 well within lip. 



Vertigo modesta corpulenta 



jf. Much'like corpulenta, but usually an additional lamella in variable stages of 

 development in the lower left-hand angle of aperture. 



Vertigo modesta parietalis 



gg. Minute, brown, shining, striate, peristome thick and brown, teeth brown, i 

 long parietal tooth, i columellar, 2 long lamellas on outer lip, lower one the 

 larger, height i .5 mm. Vertigo coloradensis 



hh. Chestnut brown, shining, whorls 5, upper 3 tapering to blunt apex, last 

 ascending toward aperture as in Pupilla blandi, i short entering parietal 

 tooth, a smaller one to right and nearer upper angle, a strong entering 

 columellar lamella, 2 long folds within outer lip, lower one the larger, 

 height 2 mm., width i . i mm. Vertigo concinnula 



ii. Very small, color dark chestnut, growth lines minute, angle of convergence 

 toward produced base and blunt apex about equal, whorls 5, 2 projecting 



