PLATE VI. 



Fig. 1. Plcctorthis ncglecta, James. A,D, brachial valves. B, pedicel valve. 

 C, view of hinge area. Series of types, James collection, No. 2:^00. 

 Chicago University. £, interior of pedicel valve. James collection. 

 No. 127. Cincinnati, Ohio, from Mount Hope bed. 



Fig. 2. Plectorthis equivalvis-pcri'agata. Primary plications of moderate 

 prominence. Brachial valve. Gurley collection. No. 8127, Chicago 

 University. Cincinnati, Ohio, from the Fairmount bed. 



Fig. 3. Plectorthis cqnivah'is-latior. Primary plications more prominent, vary- 

 ing toward Plectorthis fissicosta. Brachial valve. Gurley collec- 

 tion. No. 8127, Chicago University. Cincinnati, Ohio, from the 

 Fairmount bed. 



^ig. 4. Plcctorthis tissicosta, Hall. Wider grooves between the primary plica- 

 tions, the secondary plications added a considerable distance from 

 the beak, and occupying a distinctly lower position. Brachial valve. 

 Gurley collection. No. 8127, Chicago University. Cincinnati, Ohio, 

 from the Fairmount bed. 



Fig. 5. Plectorthis plicatclla. Hall. Brachial valves. Gurley collection. No. 

 8127, Chicago University. Cincinnati, Ohio, from the Fairmount 

 bed. 



Fig. 6. ('yclococlia sordida-mnltiplicata. With 29 to 34 plications. A, brachial 

 valve. B. pedicel valve. Gurley collection. No. 8115. C, brachial 

 valve. Chicago University. D, pedicel valve, apparently a narrow, 

 pathological specimen. James collection, No. 130, Chicago Uni- 

 versity. Cincinnati, Ohio, from the Fairmount bed. 



Fig. 7. Enlarged views of the preceding. 



Fig. S. Plcctorthis sordida. Hall. A. brachial valve. B. same, enlarged. Cin- 

 cinnati, Ohio, from the Fairmount bed. 



Fig. 9. CyclococUa crassiplicata. sp. nov. A,C, brachial valves. B, pedicel 

 valve. Cincinnati, Ohio, from the Fairmount bed. 



Fig. 10. Enlarged views of .the preceding. 



Fig. 11. Platystrophia morroivcnsis, James. A, brachial valve. B. same, en- 

 larged. Type, James collection, Chicago Universitv. Warren 

 county, Ohio, from the upper part of the Corryville bed. 



Fig. 12. Platystrophia morrozvensis, James. Form with longer hinge-line 

 named Platystrophia sintilis by Ulrich. A, pedicel valve. B, same, 

 enlarged. James collection, Chicago University. Probably found 

 associated with the preceding. 



Fig. 13. Platystrophia acuminata. James. A, pedicel valve. B, same, enlarged. 

 Type, James collection. No. 1562, Mount Auburn, at Cincinnati, 

 Ohio, probably from the IMount Auburn bed. 



Fig. 14. Platystrophia aiuiicana, James. A. pedicel valve. B. anterior view of 

 same. C. brachial valve of another specimen. T^-pes James col- 

 lection. No. 84. Chicago University. Blanche.ster. Ohio, from the 

 upper or Blanchester division of the Waynesville bed. 



Fig. 15. Platystrophia profiiiidostilcata. Meek. A.B, brachial valves. C, ante- 

 rior view. James collection. No. 186, Chicago University. La- 

 belled as types, but not the specimens figured by ]\Teck. Cincinnati, 

 Ohio, from the Fairmount bed. 



Fig. 16. Zygospira cincinnatiensis. Meek. A, pedicel valve. B, brachial valve. 

 James collection. No. 164, Chicasfo LTniversity. from a series of 

 specimens marked as types, but differing apparently from the speci- 

 men described by Meek. Cincinnati. Ohio, from the Fairmount bed. 



Fig. 17. Plectorthis equivali'is. Hall. A. lateral view. B, pedicel valve of the 

 same enlarged. Closely resembling the type described by Hall, but 

 broader. Cin'rinnati, Ohio, from the Fairmount bed. 



