PLATE XII. 



The figures on the upper "half of the plate illustrate the fauna of the Coal Measure Cherts 

 of Hocking County, Ohio. 



PAGE. 



Figs. 1-2. Discina Meekana Whitf. 488 



1. View of a lower valve from th* black chert bed 1 ?. 



2. View of a more nearly entire valve from Flint Ridge. See lower left corner of plate. 



Figs. 3-6. Spirifera (Martinia) uneata Martin 488 



,3, 4 and 5. Dorsal, ventral and front views of an internal cast from the yellow cherts. 

 6. View, enlarged to two diameters, of a partial cast from the Mack chert. The speci- 

 men shows the s-tas where the shell is retained. 



Figs. 7-9. Athyris SUBTilita Hall 488 



7-9 Dorsal, ventral and profile views of an internal cast of this species. 



Figs. 10-11. AviCULOPECTEN INTERUNEATUS M. and W 489 



10 and 11. Views of an imperfect left and right valves as obtained by gutta-percha 

 from the casts in the yellow cherts. 



Figs. 12-14. Naticopsis Ortoni Whitf 489 



12 and 13 Front and back views enlarged to two diameters, of a specimen from the 



yel ow cherts. 

 14 Diagram of the aperture, as shown by the breaking of the shell back of the aperture, 



showing the thickened shell. 



Figs. 15-17. Anthracopupa Ohioensis Whitf 491 



15. View, greatly enlarged, of the back of the shell. 



16 and 17. Similar views of the front and side showing the apertural features and 

 thickened lip. 



Figs. 18-19. Spirorbis anThracosia Whitf 492 



18 and 19. Upper and lateral views, greatly enlarged, of a specimen of the prevailing 

 form. 



Fig. 20. Nautilus Ortoni Whitf. 436 



20. Lateral view of the specimen described showing the characters of the shell. 



