PLATE I. 
Aviculopecten Cleon. 
Page 6. 
Fig - . 1. The left valve of the specimen described. The specimen is not so nearly entire as represented 
in the figure. 
Upper Helderberg g-roup. Columbus, Ohio. 
Aviculopecten ignotus. 
Page 33. 
Fig. 2. A left valve, from which the shell has been almost entirely Exfoliated. 
Upper Helderberg group. Near Victor, Ontario Co., N. Y. 
Aviculopecten (Pterinopecten?) terminalis. 
Page 32. 
Fig. 3. A left valve enlarged to two diameters. 
Upper Helderberg group. Williamsville, Erie Co., N. Y. 
Pterinopecten insons. 
Page 59. 
Fig. 4. The exfoliated left valve described, enlarged to two diameters. 
Upper Helderberg group. Western N. Y. 
Lyriopecten Dardanus. 
Page ft. 
Fig. 5 A view of an imperfect left valve, taken from a gutta-percha imjmession of the natural mould. 
The specimen is more extended on the anterior side than is represented in the figure, and 
there is an intermediate set of finer rays, also, not shown. 
Upper Helderberg group. Le Roy, N. Y. 
Pterinopecten multiradiatus. 
Page 57. 
Fig. 6. The left valve described. 
Fig. 7. A view of the impression left in the matrix. 
Upper Helderberg group. Stafford, Genesee Co., N. Y. 
Aviculopecten insignis. - 
Page 34. 
See Plates 3 and 81. 
Fig. 8. An imperfect left Valve, enlarged to two diameters. 
Hamilton group. Stafford, Genesee Co., N. Y. 
Aviculopecten pecteniformis. 
9. The original specimen described. 
Upper Helderberg group. Schoharie, N. Y. 
