PLATE VII. 



PAGE. 



MONOMERELLA NeWBERRYI 131 



Fig. 1. Dorsal view (if the internal cast described ; the lower portion of the specimen retains a little 

 of the shell. 

 2. Ventral side of the same individual. 



DiNOBOLUS COXRADI 130 



Fig. 3. Dorsal view of a specimen from Wisconsin, given for the purpose of showing the form of 

 tlie fo.ssil. the Ohio specimens being too poor for illustratiim. 

 4. Ventral view of a specimen. 



Meristina Maria 132 



Figs. 5 and 6. Cardinal and dorsal views of a specimen from Yellow Springs, Ohio, showing the fea- 

 tures of the internal casts. 



Pentamerus vextricosus 138 



Figs. 7 and 8. Dorsal and profile views of an internal cast from Yellow Springs, in the collection of 

 Prof. Hall, showing the usual features of the species. 



Pentamerus obloxgus 137 



Fig. 9. Dorsal view of a medium sized individual of the more compressed form of the species, from 

 Yellow Springs, Ohio. 



Pextamerus pergibbosus 139 



Fig. 10. Dorsal view of an internal cast of the species, from the limestones at Greenville, Ohio, 

 showing the great proportional length of the shell. 

 11. Profile of another specimen, showing the depth of the valves. Cabinet of Columbia Col- 

 lege. 



Atrypa nodostriata 133 



Figs. 12-14. Dorsal, ventral, and profile views of an internal cast, showing the usual features of the 

 specimens obtained in this condition. 



Rhynchoxella neglecta 134 



Fig. 15. Ventral view of the shell, as obtained by gutta-percha from the natural mould. 



Ryxchonella Texxesseexsis 136 



Figs. 16 and 17. Dorsal and profile views of an internal cast of the species, showing the features of 

 the species as they occur in Ohio. 



Ryxchonella pisa 135 



Figs. 18 and 19. Dorsal and profile views of a well-formed ventricose specimen. 



20. Dorsal view of a .'shorter form, with depressed convex valves. 



21. View of an elongate and veutiicose form, where the plications are unusually .angular. 



22. Outline profile of a flat-valved specimen ; probably a young specimen. 



Amphiccelia costata 140 



Fig. 23. View of thi^ right side of an individual, showing the general form of the shell and the char- 

 acter of the I'adii, as seen on the internal cast. 



