PLATE II. 
Platyceras (Orthonychia) perplexttm. 
Page 4. 
Figs. 1, 2. Views of the opposite sides of a specimen, showing the form and the irregular plications. 
Fig. 3. Lateral view of a compressed specimen, imperfect at the apex, showing the plicated surface and 
concentric striae. 
Platyceras erectum. 
Page 5. 
Fig. 4. View of the original specimen figured and described in the Fourth District Report. Upper Helder- 
berg limestone, five miles east of Buffalo, N. Y. 
Figs. 5, 6. Lateral and dorsal views of a specimen, showing a sudden expansion of the shell at the end of the 
first volution. From Cayuga, C. W. 
Figs. 7, 8. Two views of a specimen, with less closely coiled beak. From the Hamilton group at Pavil¬ 
ion, N. Y. 
Figs. 9, 10. Views of the opposite sides of a larger curved specimen. From the Hamilton group at Gen- 
eseo, N. Y. 
Fig. 11. Lateral view of a small specimen, with closely coiled apex. From the Hamilton group. 
Platyceras carinatem. 
Page 5. 
Figs. 12, 13. Lateral and dorsal views of a small specimen. Upper Helderberg limestone, Helderberg 
mountains. 
Figs. 14-16. Three views of a specimen. From near Williamsville, N. Y. 
Figs. 17-19. A large internal cast, showing several plications on the right side. From the Upper Helderberg 
group, Sandusky, Ohio. 
Figs. 20, 21. Two views of a specimen. From the Hamilton group at Canandaigua Lake, N. Y. 
Figs. 22-25. Views of a very perfect specimen, from the same locality as the preceding. 
Fig. 26. Posterior profile view of a large individual, showing an elevated obtuse carination along the back 
of the shell. From Bellona, N. Y. 
Fig. 27. Lateral view of the same, showing plications on the left side, with the sinuosities and projections of 
the margin indicated by the direction of the surface striae. 
Figs. 28, 29. Dorsal and lateral views of an internal cast, showing decided locations on each side of the 
shell, and the carination in the center. Helderberg mountains, N. Y. 
Platyceras conicem. 
Page 3. 
Figs. 30, 31. Lateral and upper views of an extremely carinate individual, with a regularly arcuate obtusely 
pointed apex. From Onondaga county, N. Y. (Reference to these figures is omitted in the text.) 
