Fig. 10. 
Fig. 11. 
Fig. 12. 
Fig. 13. 
Fig. 14, 
Fig. 15. 
SprrirER NiaGaReEnsis, Conrad. 
. 
A dorsal view; showing the lineate-plicate surface. 
Cardinal view of a portion of the pedicle-valve; showing partially 
developed deltidial plates. * 3. 
The median portion of the cardinal areas of conjoined valves; showing 
the deltarium cardinal process and crural plates. 3. 
Niagara group. Lockport, N. Y. 
SPIRIFER NOBILIS, Barrande. 
An internal cast of the pedicle-valve; showing the form of the shell. 
An internal cast of the brachial valve. 
Niagara dolomites. Wisconsin. 
SPIRIFER MESASTRIALIS, Hall. 
The exterior of a brachial valve. 
Chemung group. Southern central New York. 
199 
