EXPLANATION OF PLATE XXXI. 



Figure 1. LIMN.EA REFLEXA Say. Near WALKERI Baker. 



" 2. LIMN/EA REFLEXA WALKERI Baker. Only the center fig- 

 ure is typical. 



" 3. LIMN/EA REFLEXA EXILIS Lea. Variety. 

 " 4. LIMN/EA REFLEXA KIRTLANDIANA Lea. 

 5. LIMN/EA CATASCOPIUM Say. 



" 6. LlMN/EA PALUSTRIS NUTALLIANA Lea. 



7. LIMN/EA DESIDIO.SA Say. Variety with rounded whorls. 



" 8. LIMN/EA WOODRUFFI Baker. 



" 9. ANCYLUS SHIMEKII Pilsbry. Not so oblique as the type. 

 Enlarged. 



" 10. ANCYLUS SHIMEK.II Pilsbry. Type form. Enlarged. 



" 11. AMNICOLA LIMOSA PARVA Lea. Enlarged. 



" 12. POMA'TIOPSIS LAPIDARIA Say. Enlarged. 



" 13. PISIDIUM POLITUM Sterki. Lateral, posterior, and dorsal 

 views. 



" 14. PISIDIUM SCUTELLATUM Sterki. Lateral, posterior, and dor- 

 sal views. 



" 15. PISIDIUM WALKERI Sterki. Lateral, posterior, and dorsal 

 views. 



" 16. PISIDIUM FALLAX Sterki. Lateral, posterior, and dorsal 

 views. 



" 17. PISIDIUM PUNCTATUM Sterki. Hinge. (The Nautilus, Vol. 

 VIII, pi. ii.) Enlarged. 



" 18. PISIDIUM PUNCTATUM Sterki. The Nautilus, Vol. VIII, pi 

 ii.) Enlarged. 



" 19. PISIDIUM VARIABILE Prime. Mon. Am. Corbie., fig. 69. En- 

 larged. 



" 20. PISIDIUM CRUCIATUM Sterki. Hinge. The Nautilus, Vol. 

 VIII, pi. ii. Enlarged. 



" 21. PISIDIUM CRUCIATUM Sterki. The Nautilus, Vol. VIII, 

 pi. ii. Enlarged. 



" 22. PISIDIUM PUNCTATUM Sterki. Young specimen. 



" 23. PISIDIUM SPLENDIDULUM Sterki. Lateral and posterior 

 views. 



" 24. TESTACELLA HALIOTOIDEA Fer. Shell, enlarged. 



" 25. LIMN/EA PALUSTRIS MICHIGANENSIS Walker. 



" 26. LIMN/EA FERRISSI Baker. 

 Figures 13-16 and 22-23 are outline drawings by Dr. Sterki, xlO. 



All others, except where otherwise designated, are natural diameter. 



