PLATE IV I—Continued. 
Pholidops SUBTRUNCATA, Hilll. 
Fig. 19. The exterior of an individual; showing- the slightly flattened posterior slope and faint median 
angulation. X 4. 
Hudson River group. Lorraine, N. Y. 
Pholidops ovalis, Hall. 
Fig. 20. The external surface ; showing the charactei-istic outline and subcentral apex. X 6. 
Niagara group. Waldron, Indiana. 
Pholidops squamiformis, Hall. 
Fig. 21. The interior of a large ventral (?) valve ; showing the character of the muscular area, the median, 
anterior adductor, lobed posterior adductor, and parietal impressions. X 5. 
Niagara group. Hamilton, Ontario. 
Pholidops ovata, Hall. 
Fig. 22. An internal cast of a dorsal (?) valve ; showing the sharply defined anterior and posterior ad¬ 
ductors, and the parietal scar. X 6, 
Fig-. 23. The interior of the opposite valve ; showing the relatively small size of the muscular area. X 6. 
Lower Helderberg group. Near Clarksville, N. Y. 
Pholidops arenaria, Hall. 
Fig. 24. An internal cast of a dorsal (?) valve. From the original specimen. X 2. 
Oriskany sandstone. Knox, N. Y. 
Pholidops areolata. Hall. 
Fig. 25. An internal cast of the ventral (?) valve. X 3. 
Schoharie grit. Near Clarksville, N. Y. 
Fig. 26. An internal cast of the opposite valve. X 3. 
Schoharie grit. Knox, N. Y. 
Pholidops patina, sp. nov. 
Fig. 27. The exterior of a valve ; showing the lamellose growth-lines, crossed by fine, interrupted, radiat¬ 
ing striae. Drawn from a gutta-percha cast of a natural mould in decomposed chert. X 4. 
Fig. 28. The interior of a dorsal (?) valve. From a gutta-percha cast. X 4. 
Fig. 29. The interior of the opposite valve. X 4. 
Corniferous limestone. Be Cewville, Ontario. 
Pholidops calceola. sp. nov. 
Fig. 30. The interior of a dorsal (?) valve ; showing the terminal beak and subapical area, and the character 
of the muscular impressions. X 12. 
Corniferous limestone. Falls of the Ohio. 
Pholidops Hamilton!,®, Hull. 
Fig. 31. The exterior of the shell. X 4. 
Fig. 32. Profile of the same specimen showing the valves in conjunction. X 4. 
Hamilton group. Western New York. 
Fig. 33. The interior of a ventral (?) valve ; showing the character of the muscular impressions. X 8. 
Fig. 34. The interior of the opposite valve ; showing the muscular and parietal scars. X 4. 
Hamilton group. Canandaigua Lake, N. Y. 
Pholidops linquloides, Hall (?). 
Fig. 35. The interior of a dorsal (?) valve; showing the terminal and slightly deflected beak, the subapical 
area, and the character of the muscular scars. X 2. 
Hamilton group. Eighteen Mile Creek, N. Y. 
Pholidops oblata, Hall. 
Fig. 36. An internal cast of the dorsal (?) valve, with two deep anterior adductor scars, the posterior ad¬ 
ductors being very faintly developed, as in the preceding figure. This and figure 35 may 
represent the same species. X 4. 
Hamilton group. Carter's Mills, N. Y. 
Pholidops, compare P. Hamiltoni®. 
Fig. 37. The exterior of the shell; showing the form and outline. X 6. 
Bedford shales. Bedford, Ohio. 
