90 UNIVERSITY OF COLORADO STUDIES 



whorl constituting nearly whole shell, columella gently curved and without 

 fold, height 13 mm. Succinea nuttalliana 



^. Thin, shining, amber-colored, spire short, acute, whorls convex, last marked 

 by growth wrinkles, light callus on columella, aperture f length of shell, 

 expanding below and exhibiting volutions to apex, height 15 to 21 mm., 

 width 7 to 9 mm. Succinea haydeni 



gg. Whitish horn-colored, pellucid, shining, delicately striate, marked irregularly 

 with impressed spiral lines, aperture oval, angular above, height 1 8 to 20 mm. 



Succinea salleana 

 2. Wider in proportion to height. 



aa. Whorls full and rounded, growth wrinkles irregular, interspaces often 

 crossed by parallel spiral lines. Succinea grosvenori 



bb. Similar to avara but more compact, shorter in proportion to width. 



Succinea stretchiana 



b. Aperture \ length of shell, shell oval, highly polished, whorls 6, gradually increasing 

 in size, growth lines very fine, peristome simple, length 5.5 to 6 mm., width 2 . 25 mm., 

 an vumiistakable species. Cochlicopa lubrica 



c. Aperture very small, shell small, spire long in proportion to aperture, generally 

 cylindrical with obtusely rounded apex, whorls numerous, not usually increasing 

 much after the first 2 or 3. 



I. Whorls 6 or 7, except B. pentodon. 



aa. Brownish horn color, shell tapering regularly from body whorl to apex, 

 growth Unes fine, base produced, aperture toothless, umbilicus deep and 

 open, persistome reflected, height 5 mm., width 2 mm. 



Pupoides marginatus 



bb. Horn color, small, cyclindrical, irregularly ribbed, aperture toothless^ 

 peristome narrowly reflected and white, \imbilicate, umbiHcus bounded by 

 an angle, height 3 .5 mm., width i .6 mm. Pupoides hordaceus 



cc. Dark chestnut or bay, lower 4 whorls about equal diameter, growth lines 

 fine, aperture usually toothless, umbilicus perforate, persistome somewhat 

 reflected, height 4 mm., width 1.5 mm. Pupilla muscorum 



dd. Light brown, last whorl ascending and rapidly expanding toward aperture, 

 external callus separated from subreflected peristome by deep constriction, 

 teeth obtuse, i parietal, i columellar, i far within base of aperture, height 

 3 mm., width i .5 mm. Pupilla blandi 



ee. Brownish horn color, cylindrical, whorls gradually increasing, striated 

 rugulose, coarser near aperture, lip abruptly but narrowly everted, teeth 

 white, parietal deep seated, long and spiral, columellar perpendicular along 

 columella, palatal (the inferior) strong often vnth threadlike prolongation 

 inward, height 2.6 mm., width i .3 mm. Pupilla sonorana 



f. Light horn color, inflated, vitreous, shining, smooth, growth lines crowded, 

 first 3 whorls increasing rapidly, last 3 about equal, i single or double 

 parietal lamella, a massive tooth on columellar wall far within, i at lower 



