I'LATK LXXXV— Cniilinucd. 



Ptychoptekia Beecheiu. 



P&ae Hi. 

 Kii;. 21. All entire li'ft valvo sliowiiij;' its "-ibboiis anil arcnate form, 

 l-'iff. 22. .V rij.'-ht valvo of this sjiocies. 



Chemung- group. Jrarnti. Pa. 



Ptyctioptekia I-AIA. 



I'aye lir,. 

 Fig. 23. An entire left valvi'. 



F\g. 24. A larger left valve. 



Fig. 2"). A right valve showing its comparatively strong alar I'ol.l. 

 Chemung group. If'aireit. Pa. 



Ptycjiopteria alata. 



Pajro 139. 

 See Plate 23. 



I'ig. 20. The posterior half of a left valve, showing the subangnl.u- posterior slope. 

 Chemung group. >ia1amania, N. T. 



Ptychoptkria Eucrate. 



Page 133. 

 See Plate 23. 

 Fig. 27. A left valve of this species. 

 Fig. 28. A small left valve. 



Chemung group. Pannina, N. Y. 



PtYCHOPTERIA (lAI.f.NE. 

 Page 1«. 

 Fig. 29. A left valve flattened by pntssure. 



Fig. 30. A smaller left valve preserving the normal proportions of the species. 

 Fig. 31. The right valve of a specimen preserving both valves. 

 Chemung group. JVarrea, Pa. 



Ptychopteria Thalia. 



p.i.tfc us. 

 Fig. 32. A small right valve. 



Fig. 33. A meilium sized left valve showing the short gibbous form of the shell. 



Chemung group. Alleghany Sjirings, Warren Co. . Pa . 



PlY-CnOPTERIA TRIGONALIS. 



I'a^'C- 140. 

 Fig. 34. A small left valve showing the form and chai-aeters of the species. 

 Fig. 35. A large imperfect left valve. 



Chemung group. Panama, N. Y. 



Ptychopteria Vanuxemi. 



Page 151. 

 Fig. 3C. A portion of a large left valve, showing the peculiar form of the bocly and the surface charactera. 

 Chemung gi'tuip. IVarren, Pa. 



Ptychopteria lobata. 



Page ISO. 

 Fig. 37. A left valve showing the short form of the valve .and the strong alar plication. 

 Chemung group. IVarrni, Pa. 



Ptychopteria peui.ai \. 



Pajt8,147. 

 Fig. 3.S. A right valve of this species. 



Fig. 39. A left valve showing the form and surface markings. 



Chemung grouj). Warren, Pa. 



