280 



PLATE VIII 



Page 



Figs. 1 to 3. Productus cora d'Orbigny 180 



Fig. 1. Ventral valve of specimen of average size. Lower 



Mercer limestone: Muskingum County, near Fairview 



School, Locality 45. 

 Fig. 2. Dorsal valve. Lower Mercer limestone: Licking 



County, Flint Ridge, Locality 47. 

 Fig. 3. Exterior of dorsal valve. Same locality. 



Figs . 4 , 5 . Productus semireticulatus ( Martin) var 181 



Lower Mercer limestone: Muskingum County, Symmes 



Creek, Locality 29. 

 Fig. 4. Ventral valve showing the fine, regular, concentric 



markings in the umbonal region. 

 Fig. 5. Ventral valve of another specimen. 



Fig. 6. Productus semireticulatus (Martin) 181 



Ventral valve of a specimen of typical size. Lower Mercer 



limestone: Muskingum County, Blunt Run, Locality 27. 



Fig. 7. Pustula symmetricus (McChesney) 183 



Lower Mercer member: Perry County, Somerset, Loca^ty 



35. 

 External mold of dorsal valve showing the trifid cardinal 



process. Hyde collection 828. 



Fig. 8. Pustula pertenuis (Meek) 182 



After Mark. Conemaugh formation: Ames limestone, 



New Concord, Ohio. 

 Ventral valve. x2 



Fig. 9. Pustula punctatus (Martin) 183 



After Mark. Conemaugh formation: . Cambridge lime- 

 stone, Cambridge, Ohio. 

 Ventral valve. 



Figs. 10 to 13. Composita subtilita (Hall) 192 



Lower Mercer limestone: Muskingum County, southeast of 



Frazeysburg, Locality 43. 

 Fig. 10. Dorsal valve. 

 Fig. 11. Ventral valve. 

 Fig. 12. Lateral view. 

 Fig. 13. Front view. 



