PLATE IX. 



TORYNIFER CRITICUS, Hall. 



Page 359. 

 Fig. 1. A fragment of the pedicle- valve with vrell-defined cardinal area, 

 prominent teeth, convergent dental lamellae, forming a distinct spondy- 

 lium, supported by a median septum. X 2. 

 St. Louis group . La Rue, Kentucky. 



Rhynchospira scansa, Hall. 

 Page 360. 

 Fig. 2. A viev^^ of the exterior of the pedicle-valve, showing a median sulcus 

 similar to that occurring in typical representatives of the genus . 

 Waverly group. McKean county, Pennsylvania. 



Athyris densa, Hall. 



• Page 358. 



Fig. 3. The interior of a small but thickened pedicle-valve; showing the broad 

 cardinal slopes, the deep pedicle-cavity and relatively large muscular 

 impressions. 



Figs. 4, 5. Dorsal and profile views of conjoined valves; showing the contour 

 of the shell, the foramen and broad cardinal slopes of the pedicle- valve, 

 the median elevation and low marginal sulcus of the brachial valve. 

 St. Louis group. Colesburgh, Kentucky. 

 Fig. 6. The interior of a larger pedicle- valve; showing a faint median ridge. 

 Fig. 7. The interior of another pedicle- valve, showing an umbonal thickening 

 of the shell, and the division of the muscular area. 

 St. Louis group. Washington county, Indiana. 

 Fig. 8. The interior of a pedicle- valve with relatively small muscular area and 

 linguate extension of the anterior margin, which is much foreshortened 

 in the figure . 

 St . Louis group . Lanesville, Indiana. 

 Fig. 9. The interior of a pedicle- valve, showing the details of the muscular 

 structure . 

 St. Louis group. Colesburgh, Kentucky. 



Seminuli Rogersi, Hall. 

 Page 359. 

 Fig. 10. A dorsal view of an internal cast. 



Fig. 11. A ventral view of a similar specimen; showing the cast of the 

 pedicle-cavity and muscular scars . 



Fig. 12. Cardinal view of the same specimen. 

 Fig. 13. A profile of the specimen represented in Fig. 10. 

 Pendleton sandstone. Pendleton, Indiana. ' 



390 



