PLATE XXIII. 
Leptodesma naviforme. 
Page 200. 
See Plate 22. 
Pig. 1. A right valve showing the characters of the shell. 
Chemung group. Near Ithaca, N. Y. 
Actinopteria perstrialis. 
Page 11S. 
See Plate 84. 
Pig. 2. A left valve. 
Pig. 7. A right valve of a larger example. 
Chemung group. Ithaca, N. Y. 
Pig. 
3. The left valve described. 
Chemung group. 
Actinopteria delta. 
Page 121. 
Ithaca, N. Y. 
Actinopteria epsilon. 
Page 122. 
Fig. 4. A small left valve. 
Figs. 5, 6. Two left valves referred to this species with some doubt on account of their finer surface radii. 
Fig. 8. An impression of a left valve, retaining that of the right valve beneath it in the centre, thus show r - 
ing partly the features of both. 
Chemung group. Ithaca, N. Y. 
Actinopteria zeta. 
Page 123. 
See Plate 84. 
Fig. 9. A right valve showing the form and surface ornamentation, with two oblique lateral teeth. 
Chemung group. Ithaca, N. Y. 
Ptychopteria expansa. 
Page 152. 
Fig. 10. The left valve described showing the form and surface ornamentation. The body is represented 
as too narrow and there should be a slight furrow limiting the wing. 
Fig. 11. An enlargement of the surface from the anterior umbonal slope, showing the direction of the radii. 
Chemung group. Smethport; Pa. 
Ptychopteria Proto. 
Page 129. 
Figs. 12,14. Two left valves. The wings in each one should be limited by a slight furrow. 
Chemung group. Near Smethport, Pa. 
