PLATE XXIII— Continued. 



PTTCHOPTEBIA >I\M ISA. 



Page 130, 



See Plate 85. 



Fig. 13. A left valve showing the form and surface characters. The wing should be limited by a shallow 



furrow. 



Chemung gTOup. Neai '• . Pa. 



LEFroDESMA Mentor. 



Page 205. 

 Bee Plate StO. 

 Fig. 15. An imperfect right valve supposed to belong to this species from its association. 

 Chemung group. Near Smethport, Pa. 



PtYCHOPTERIA Sad. 

 Page 132. 



See Plat.- 85. 

 Pig. 16. A left valve of medium size. The fold and furrow of the wing should be represented as stronger. 

 Fig. 23. An associated tight valve. 



Chemung group. Panama, Chautauqua Co., X. Y. 



Ptycik >ptei;i a Salamanca. 



Page LSI. 

 Figs. 17. 18. Two left valves showing the form of the shell and surface characters. Fig. IS should show an 



alar fold similar to fig. 17. 

 Fig. 19. A cardinal view of the specimen, fig. 18, showing the relative convexity of the valves and the com- 

 parative elevation of the beaks. 

 Fig. 20. The right side of a specimen preserving both valves partly opened. 

 Chemung group. Near Salamanca, -V. 1". 



Ptychopteria ALATA. 



Page 139. 



See Plate 85. 

 Pigs. 21, 22. Two small right valves. 

 Figs. 25, 26. Two larger characteristic eight valves. 



Chemung group. Salamanca, N. Y. 



Ptychopteiua Eucrate. 



Page 13S. 

 See Plate 85. 



Fig. 24. The right side of a specimen preserving both valves. * 

 Chemung group. Panama, N. Y. 



ECTENODESMA BIROSTRATUM. 



Pilge 24-2. 



See Plate 84. 

 Pig. 27. A right val\ e referred to this species, showing the form, surface ornamentation and strong, oblique 

 lateral tooth. 



Chemung gi p. Four miles north of Chenango Forks. S. Y. 



Figs. 28-30. Three left valves in different degrees of preservation, showing some variation in form and 

 surface markings. 



Chemung group. Franklin, Belaxoart Co., N. 1". 



