GASTROCOPTA, NORTH AMERICA, WEST INDIES. 39 



6 1 . Shell dextral. 



c. Columellar lamella running forward on the 

 parietal wall in the position of an infrapari- 

 etal lamella; lower palatal and basal folds 

 very deeply immersed; neck gibbous; peri- 

 stome continuous. 



d. Length about 2 mm. G. ashmuni, no. 9. 

 d 1 . Length 1.6 to 1.8 mm. 



G. ashmuni minor, no. 9a. 



c 1 . Columellar lamella normal in position, not 

 running forward on the parietal wall, turned 

 down at the inner end; peristome scarcely or 

 not continuous; palatal plicae visible in a 

 front view; basal fold well developed. 



d. A very strong, white crest behind the 

 lip; columellar lamella having a long, 

 vertical inner portion; length about 

 1.75 mm. G. holzingeri, no. 3. 



d 1 . No distinct crest on the neck; length, 

 2 mm. or more; Arizona. 



G. cochisensis, no. 10. 



a 1 . Inner end of the parietal lamella curving outward very 

 little; teeth not large; ends of peristome well separated; 

 angular lamella low. 



&. Columellar lamella very short; lower palatal plica 



rather deeply placed; basal fold minute, rarely 



wanting; Arizona. G. oligobasodon, no. 11. 



6 1 . Columellar lamella longer ; lower palatal less deeply 



placed; no basal fold; central Mexico. 



G. prototypus, no. 12. 



b 2 . Like prototypus, but with a well-developed basal 

 fold ; Guatemala. G. p. basidentata, no. I2a. 



a 2 . Inner end of the parietal lamella not distinctly curving 

 towards the periphery; palatal and basal folds well de- 

 veloped, visible in a front view. 



&. Entire columellar lamella horizontal; margins of 

 peristome rather remote ; Arizona. 



c. Columellar lamella simple; parietal lamella 



