PLATE XXVII—Continued. 
Syringothyris subguspidatus, Hall. 
See Plate 26. 
Fig. 18. A front view of the pedicle-valve ; showing its exterior and elevation, with the baso-lateral mar¬ 
gins of the brachial valve. 
Keokuk group. Keokuk, Iowa. 
Genus SPIEIFER, Sowerby. 
Page 1. 
Spirieer Wortheni, Hall. 
Fig. 19. A view of the original specimen. 
Fig. 20. An enlargement of the external surface of the shell. 
Upper Helderberg group. Near Hamburg, Illinois. 
