PLATE XLV. 



PAGB. 



Figs. 1-2. Byssonychia pr.-ecursa, u. sp 633 



1. Cast of the interior of a right valve of the usual size. The hinge line often is 



longer. 



2. Anterior view of same and of a left valve belonging to the Illinois State Museum. 



Loraine shales, Eoraine, New York. 



Figs. 3-4. Byssonychia richmondensis, n. sp 632 



Anterior and lateral views of a cast of the interior of the average size and proportions. 

 Near top of Cincinnati group, Richmond; Ind. 



Figs. 5-7. Byssonychia cuetrata, n. sp 632 



5. Right valve of the usual size. The specimen preserves some of the test but is most- 

 ly a cast of the interior. 



6 and 7. The anterior portion of the hinge of a left and aright valve, showing the car- 

 dinal teeth and the channel-like ligamental area. Upper beds of the Cincinnati 

 group. Waynesville, Ohio. 



Figs. 8-9. Byssonychia acutirostris, n. sp. (See also Plate 46, Fig. 10) 634 



8. The hinge and the upper part of the anterior margin of a small testiferous speci- 



men, x 2. The figure shows the small cardinal teeth, ligamental area and the 

 plicated character of the margin of the byssal opening. Posterior lateral teeth 

 seem to be wanting in this species. 



9. Anterior view of same specimen, natural size. Middle beds of the Cincinnati group, 



Cincinnati, Ohio. 



Figs. 10-12. Byssonychia obesa, n. sp 630 



10-12. Three views of a cast of the interior of medium size, showing the usual rounded 

 form, the depression surrounding the small byssal opening, and other charac- 

 ters of the species. Some specimens are proportionally a little higher. Upper 

 beds of the Cincinnati group, Richmond, Indiana. 



Figs. 13-15. Byssonychia suberecta, n. sp 634 



13. An imperfeet testiferous right valve of the average size showing the erect form, 



and the wide angle formed by the hinge line and the anterior margin. 



14. The anterior part of the hinge of a left valve. 



15. Anterior views of the two valves. Upper beds of the Cincinnati group, Versailles 



Indiana. 



