PLATE XI,VII. 



PAGE 



Fig. 1. Eridonychia apicalis, n. sp 639 



Interior of a left valve as shown in a gutta-percha impression of a cast of the in- 

 terior. Middle beds of the Cincinnati group, Newport, Kentucky. 



Fig. 2. Eridonychia paucicostata, n. sp 640 



An average left valve of this species. Middle beds of the Cincinnati group, Coving- 

 ton, Kentucky. 



Fig. 3. Eridonychia crenata, n. sp 640 



A left valve showing the greatly attenuated beaks and the wavy character of the ventral 

 outline. Upper beds of the Cincinnati group, Waynesville, Ohio. 



Figs. 4-5. Bysonychia? byrnesi, n. sp 635 



4. Gutta-percha impression of a natural mold of the exterior of a right valve. The 



outline of this specimen is a little unusual in the post-dorsal region. 



5. A left valve of the usual size and form. Lower beds of the Cincinnati group, Cov- 



ington, Kentucky. 



Fig. 6. Opisthoptera laticostata, n. sp 646 



The right side of a somewhat imperfect cast of the exterior. Upper beds of the Cin- 

 cinnati group, near Waynesville, Ohio. Collection of the Ohio State Uni- 

 versity. 



Fig. 7. Opisthoptera ampla, n. sp . 647 



View of the imperfect specimen described. It is a cast of the interior of a left valve. 

 , Middle beds of the Cincinnati group, Cincinnati, Ohio. 



Fig. 8. Lyrodesma subplanum, n. sp 683 



Partial cast of the interior of a large right valve. Lower beds of the Cincinnati, 

 group, Covington, Kentucky. 



Fig. 9. Lyrodesma conradi, n. sp 684 



Sharply denned cast of the interior, showing the muscular scars and the sinuate 

 pallial line very clearly. Lower beds of the Cincinnati group, Covington, Ken- 

 tucky. 



Figs. 10-12. Technophorus punctostriatus, n. sp 685 



10. Right valve of the natural size. 



11. Castofthe interior of a left valve. 



12. The original of Fig. 10 magnified two and one-half diameters to show the regular 



puncto-lineate surface marking. Middle beds of the Cincinnati group, Cov- 

 ington, Kentucky. 



Figs. 13-14. Technophorus yoldiiformis, Ulrich 685 



13 The original type of this species, x 2. The specimen is preserved in soft shale as 



a partial cast of the interior. 

 14. The same valve together with a right valve found in the same block of shale. Lower 



beds of the Cincinnati group, Covington, Kentucky. 



