PLATE XXI—Continued. 
Genus SPIRIFEE, Sowerby. 
Page 1. 
Spikieer Eudora, Hall. 
Fig. 19. An internal cast; showing the impressions of the dental plates. 
Fig. 20. A profile of the same. 
Niagara group. Racine, Wisconsin. 
Fig. 21. The exterior of the pedicle-valve; showing the lineate surface. 
Fig. 29. An enlargement of the surface of the same specimen. 
Niagara group. WaldroJi, Indiana. 
Spiriter macropleura, Conrad. 
Fig. 22. A doi-sal view of a normal, mature individual; showing the surface characters. 
Lower Helderberg group. /Schoharie, iV. Y. 
Fig. 27. An enlargement of the surface of the same specimen. 
Fig. 2R. The interior of a portion of the pedicle-valve ; showing the callosity of the delthyrium. 
Fig. 24. An internal cast of the pedicle-valve; showing the impressions of the pedicle, adductor and 
diductor muscles. 
Lower Helderberg group. The Helderhergs, N. Y. 
