380 AMERICAN SPECIES OF VERTIGO. 



Fig. t. Aperture of Vertigo tridentata Wolf; showing a trace of the primary lam- 

 ella E. 



Fif. 5. Diagram of the aperture of Vertigo ovata Say; showing primary lamellae, 

 designated by letters, A on the body, B on the pillar, C at the base of the 

 pillar, D and E on the outer lip. Also the secondary or accessory laniellte 

 designated by figures 1, la, and 2, on the body; 3, 4, 5, and 6 on the outer 

 lip. There are sometimes two secondary denticles between C and D. 



Fig. (i. Vertigo ovata Say, profile. 



Fig. 7. Vertigo ovata Say ; view of the base; the dotted lines opposite x represent 

 t1i>- undulations shown by a section of the last whorl. 



Fig. 8. Vertigo alpestris Alder ; European. Base as in Fig. 7. 



Fig. ( J. Vertigo alpestris Alder, in profile. 



Fig. 10. Angustula milium Gould; outline of the aperture showing the lamellae. 



Fig. 11. Angustula venetzii Charpentier; diagram of the aperture showing the lamellae. 



Fig. 12. The same, showing the position of the lamellae as seen through the shell on 

 the left side. 



Fig. 13. Angustula milium Gould diagram showing the lamellae, as seen through the 

 shell from the right side, for comparison with figure 12. 



