56 GASTBOCOPTA, NORTH AMERICA, WEST INDIES. 



d 1 . Smaller, 2 to 2.2 mm. long, 0.9 mm. 

 wide; Bimini Islands. 



G. p. biminiensis, no. 22a. 

 a 1 . Lip thin, not calloused within. 



b. Having 5 well-developed teeth, a basal fold present. 

 c. Diam. usually over 1 mm., about 2.5 mm. 

 long; brownish. 



d. No crest behind the lip; parietal tooth 

 not strongly bifid, no infraparietal tu- 

 bercle. G. servilis, no. 21. 

 d 1 . A narrow crest; parietal bifid; an infra- 

 parietal nodule often developed. 



G. riograndensis, no. 20. 

 c 1 . Diam. 1 mm. or less; length 1.5 to 2.6 mm. 



d. Parietal strongly bifid; a callous or 

 tooth below the columellar lamella. 

 e. An infraparietal nodule present. 

 G. polyptyx, no. 25. 

 e 1 . No infraparietal tooth. 



G. barbadensis, no. 24. 



d 1 . Parietal sinuous or emarginate, but not 

 distinctly bifid. 



e. Diam. one-third the length; Cura- 

 cao. G. longurio, no. 23. 

 e 1 . Somewhat wider. 



G. pellucida and varr., no. 22. 

 d 2 . Parietal simple and straight, angular 

 wanting or minute. 



e. Ovate-conic, 1.2 x 1 mm.; peri- 

 stome not expanded; Ohio. 



G. carnegiei, no. 6. 



e 1 . Cylindric, 1.7 x 0.9 mm.; peri- 



stome expanded; Arizona, New 



Mexico. G. p&sbryana, no. 7. 



c*. Having 4 strongly-developed teeth, the an- 



gulo-parietal almost simple; no basal fold; 



shell albino; New Mexico and Arizona. 



G. qitadridens, no. 16. 



