PLATE XLIX. 



PAGE. 



Figs. 1-5. Opisthoptera casei, Meek and Worthen 643 



I. Gutta percha impression of a natural mold of the exterior of a large left valve. 



Upper beds of the Cincinnati group, Marion county, Kentucky. 

 '2-4. Three views of a nearly perfect cast of the interior of a small shell. Richmond, 

 Indiana. 



5. The left side of a larger cast of the interior from the same locality. The specimen is 



imperfect posteriorly but shows the muscular scars and pajlial line very dis- 

 tinctly. 

 Figs. 6-8. Opisthoptera obuqua, n. sp 646 



6. Dorsal view of the largest and best cast of the interior seen. Upper beds of the 



Cincinnati group, Richmond, Indiana. 



7. The right side of same with some remains of the radial striae. Generally the sur- 



face markings are not distinguishable on the casts. 



8. Anterior view of same. 



Figs. 9-11. Opisthoptera ai/ternata, n. sp 644 



9. Left side of a small cast of the exterior. The specimen is slightly distorted. (See 



p. 645, fig.— e.) 



10. Anterior view of same x2, showing the byssal opening and bifurcating costse. 



II. Anterior view of a large cast of the exterior believed to belong to this species. The 



surface markings in this specimen are much as in figure 15 of this plate, and it is 

 possible that it is really a distorted example of O. fissicosta. Upper beds of 

 the Cincinnati group, Waynesville, Ohio. 



Figs. 12-14. Physetomya acuminata, n. gen. et sp 693 



Anterior, cardinal and lateral views of the specimen described. Middle beds of the 

 Cincinnati group, Cincinnati, Ohio. 



Fig. 15. Opisthoptera eissicosta, Meek 643 



Gutta percha impression from a natural mold of the exterior of a right valve, showing 

 the form of the shell and the fissicostate surface markings. Upper beds of the 

 Cincinnati group, Clarksville, Ohio. 



Fig. 16. Opisthoptera notabius, n. sp 648 



Gutta percha impression from a natural mold of the exterior of a left valve. The spec- 

 imen is imperfect at the posterior extremity of the wing. Middle beds of the 

 Cincinnati group, Cincinnati, Ohio. 



Figs. 17-20. ProThyris sp (compare P. meeki, Winchell). 



17-28. Three views of a large specimen. 



20. Left side of a smaller, example. 



These two and other specimens were found by myself several years ago on the hill 

 quarry dumps west of Covington, Kentucky. How they came there is not known, 

 but I have satisfied myself that they do not belong to the Cincinnati group. As 

 the species is closely related to if not identified with Winchell's P. meeki, and as 

 the shells were evidently imbedded originally in a fine-grained, bluish-gray sand- 

 stone, it is not improbable that they belong to the Waverly of Ohio. 



