Fig. 9. A section of the same valve nearer the hinge and below the edge of 
the transverse plate. The free portion of the syrinx is seen to be 
open on the inner side. 
Keokuk group. New Providence, Indiana. 
SyRincoTHyrRis Ranpawu, Simpson. 
Fig. 10. A cardinal view of an internal cast; showing the impression of the 
deltarium and the cavity left by the syrinx. 
Fig. 11. Cardinal view of a pedicle-valve retaining the convex deltarium. 
Waverly group. Warren, Pennsylvania. 
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