PLATE LII. 



PAGE 



Figs. 1-2. Psiloconcha grandis, n. sp 665 



The left side and a dorsal view of an excellently preserved cast of the interior. Upper 

 beds of the Cincinnati group, Wayuesville, Ohio. 



Figs. 3-4. Psiloconcha elliptica, n. sp 667 



3. A testiferous example of a right valve. 



4. The right side of a cast of the interior, showing muscular scars and pallial line. 

 Upper beds of the Cincinnati group, Clarksville, Ohio. 



Figs. 5-7. Psiloconcha subovalis, Ulrich 666 



5. Imperfect left valve from the lower beds of the Cincinnati group. Collection of 



Mr. George Ashermau. 



6. A small specimen from the same horizon near Covington, Kentucky. 



7. Right side of the original type of the species. Middle beds of the Cincinnati 



group, Morrow, Ohio. 



Figs. 8-9. Psiloconcha minima, n. sp 669 



The right side of the specimen described. It is a sharply marked cast of the interior 

 and shows the anterior muscular scar but no trace of either the posterior scar 

 or the pallial line. Lower beds of the Cincinnati group, Covington, Kentucky. 



Fig. 10. Psiloconcha tenuistriata, n. sp 668 



The right side of an imperfect testiferous example, x'2. On a small space beneath the 

 beak, I have attempted to give an idea of the extreme delicacy of the concentric 

 lines. Lower beds of the Cincinnati group, Covington Kentucky. 



Figs. 11-12. Psiloconcha inornata, n.sp 667 



11. Cast of the exterior of a right valve. 



12. A specimen retaining both valves in position, the upper one showing the normal 



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



Figs. 13-14. Psiloconcha subrecta, u. sp 667 



_ The lelt side and a dorsal view of a cast of the exterior. Upper beds of the Cincinnati 

 group, Wayuesville, Ohio. 



Figs. 15-16. Psiloconcha sinuata, n. sp 668 



Casts of the exterior of a right and a left valve Middle beds of the Cincinnati group, 

 Cincinnati, Ohio. 



Figs. 17-19. COLPOMYA CONSTRICTA, n. sp 659 



17 and 18. Interiors of a left and right valve, showing the hinge and muscular im- 

 pressions. These two figures suffered somewhat in the reproduction. 

 19. Exterior of a large right valve. Uppermost beds of the Trenton group, Frankfort, 

 Kentucky. 



Figs. 20-21. Modiolodon obtusus, n. sp 654 



Impressions of the exterior of a left and a right v^lve of the typical form of this species, 

 both showing traces of the anterior muscular scar. Middle beds of the Cincin- 

 nati group, Cincinnati, Ohio. 



