PLATE LXXXV. 



Ptychoptebia Thetis. 



Pase 135. 

 Figs. 1-3. Three left valves showing' some variation in form and obliquity. 

 Fig. 4. A I'ight valve referred to this species. 



Chemung group. Panama. N. Y. 



Ptyciiopteria gibbosa. 



Page UO. 

 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. 



Ptychop teria falcata. 



Paj?e 13G. 

 Fig. 6. An entii-e left valve, showing the form and surface markings. 

 Pig. 7. A smaller example of the same valve. 



Chemung gi'oup. Alleghany Spring.s, Warren Co., Pa. 



Pttchopteria sinuoja. 



Page l:iO. 

 See Plate 23. 

 Fig. 8. A left valve showing the oblique cardinal and latei-al teeth. 

 Chemung group. Warren. Pa. 



PfiCIlOPTERIA El 'DOR A. 



Page i:t8. 

 Fig. 9. A left valve of this species showing its elongate form. 

 Chemung gi-oup. Panama, N. F. 



Ptychopteria et,oxoat.\. 



Page 141. 

 Fig. 10. A carilinal view of a specimen preserving both valves. 

 Fig. 11. The ventral view of a smaller .specimen with the v.ilves closed. 

 Fig. 12. A large right valve of this species. 

 Fig. 13. The left valve of the specimen tig. 10. 



Chemung gnuip. Panama, N. Y. 



Ptychopteria Sao. 



Page r.'.-i. 

 See Plate 23. 

 Plf;, 14. A small left vahe. 

 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 compai-ed with the right. 

 Fig. 18. The \-entral 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, W. Y. 



Ptychopteria .spatulata. 



Page lU. 

 Fig. 20. A left valve showing its large size and broad elongate form. 

 Chemung group. Warren, Pa. 



