PLATE LXXXV. 
Ptychopteria Thetis. 
Page 135. 
Figs. 1-3. Three left valves showing some variation in form and obliquity. 
Fig. 4. A right valve referred to this species. 
Chemung group. Panama, N. Y. 
Ptychopteria gibbosa. 
Page 149. 
Fig. 5. A left valve showing the large anterior end and short wing, with the broadly gibbous body of the 
valve. Chemung group. Warren, Pa. 
Ptychopteria falcata. 
Page 13(5. 
Fig. 6. An entire left valve, showing the form and surface markings. 
Fig. 7. A smaller example of the same valve. 
Chemung group. Alleghany Springs, Warren Co., Pa. 
Ptychopteria sinuosa. 
Page 130. 
See Plate 23. 
Fig. 8. A left valve showing the oblique cardinal and lateral teeth. 
Chemung group. Warren, Pa. . 
Ptychopteria Eudora. 
Page 138. 
Fig. 9. A left valve of this species showing its elongate form. 
Chemung group. Panama, N, Y. 
Ptychopteria eeongata. 
Fig. 10. A cardinal view of a specimen preserving both valves. 
Fig-. 11. The ventral view of a smaller specimen with the valves closed. 
Fig. 12. A large right valve of this species. 
Fig. 13. The left valve of the specimen fig. 10. 
Chemung group. Panama, N. Y. 
Ptychopteria Sao. 
Page 132. 
See Plate 23. 
Fig. 14. A small left vhlve. 
Fig. 15. The left valve of a larger example. 
Fig. 16. A specimen of medium size. 
Fig. 17. The cardinal view of a small individual, showing the prominent beak and umbo of the left valve 
as compared with the right. 
Fig. 18. The ventral view of a specimen preserving both valves. 
Chemung group. Panama, N. Y. 
Ptychopteria Spio. 
Page 137. 
Fig. 19. A left valve of this species. 
Chemung group. Panama, N. Y. 
Ptychopteria spatulata. 
Page 144. 
Fig. 20. A left valve showing its large size and broad elongate form. 
Chemung group. Warren, Pa. 
