PLATE I— Continued. 



AVICULOPECTEN PEINCEPS. 



Page 1. 

 See Plates 5, e, 24 and 81. 

 Fig:. 10. A left valve. 



Upper Helderberg group. Falls of the Ohio. 

 Fig. 11. A larger left valve of this species. The hinge-line should be represented as straight. 

 Upper Helderberg group. Bearffrass creek, Ky. 



Pterinopecten dignatus. 



Page 6-.'. 

 Fig. 12. A left valve, enlarged to two diameters, showing the form and surface characters. 

 Fig. 14. A specimen retaining both valves, enlarged to two diameters, showing their compai'ati\e form and 

 surface oniamentation. The anterior ear of the right val\e hiis much strongei- rays than 

 represented. 

 Fig. 15. An imperfect left valve, natiu'al size. 



Marcellus shale. Blonmfield, Onlariu Co., N. Y. 



Ptekinopecten l^tus. 



Page 63. 

 Fig. 13. The left valve of the specimen described, X 2. The umbo shoidd be represented as free from 

 radii, and concentrically wrinkled. 



Marcellus shale. BloomfieUl, Ontario Co., N. Y. 



Pterinopecten exfoliatus. 



Page 61. 

 See Plate 83. 

 Fig. 1(5. A medium sized left valve of this species. 



Limestone of the Marcellus shale. Avon, N. Y. 

 Fig. 17. A large left valve, with the test more exfoliated than the pi'eceding. ^ 



Limestone of the Marcellus shale. Vimma, Ontario Co., N. Y. 



Aviculopeoten (Pterinopecten ?) invalidus. 



Page 31. 

 See Plate 82. 

 Fig. 18. A left valve, X 2. Hg. 21, plate 82, gives a more entire outline of this species and of the natural 

 size. 



Marcellus shale. Cherry Valley, iV. Y. 



