PLATE XX— Continued. 



Cyphaspis minuscula. 



Page 140. 

 See Plate 24. 

 Fig. 17. An entire individual, enlarged to three diameters'. The outline of the pygidium is incoiTectly 

 represented, and through an oversight has been left untinted. The cheek spines are also 

 made to appear shorter than in the specimen. 



Corniferous limestone. Schoharie, Schoharie county. 



Proetus Vebneuili. 



Page 108. 

 Fig. 18. The original specimen, showing a portion of the thorax, the pygidium, and the characteristic 



nodes on the pygidial border. Enlarged to three diameters. 

 Fig. 19. Profile view of the same. 



Upper Helderberg limestone. Williamsville, Erie county. 



Proetus crassimarginatus. 



Page 99. 

 See Plates 22 and 25. 

 Fig. 6. The pygidium as a cast of the internal surface, showing the doublure and the obscure annulat ions. 

 This usual condition of preservation in the Schoharie grit. 



Schoharie grit. Near Qlarksville, Albany county. 

 Fig. 7. Profile view of a larger pygidium, an internal cast, upon which the ambulations are obsolete 

 Fig. 8. Dorsal view of the same. 



Schoharie grit. Albany county. 

 Fig. 20. An imperfect glabella with the crust nearly all removed. 

 Fig. 21. Profile view of the same. 



Corniferous limestone. Falls of the Ohio. 

 Fig. 22. A very large glabella. 



Upper Helderberg limestone. Near Clarence, Erie county. 

 Fig. 23. The left free cheek. 

 Fig. 24. Lateral view of the same. 



Upper Helderberg limestone. Near Clarence, Erie county. 

 Fig. 25. A small pygidium. 



Corniferous limestone. Falls of the Ohio. 

 Fig. 26. A larger pygidium, showing the characteristic curves of the axial annulations. 



Corniferous limestone Falls of the Ohio. 

 Fig. 27. A large pygidium. The drawing fails to represent the proper degree of rotundity. 



Upper Helderberg limestone. Cayuga, Province of Ontario. 

 Fiff. 28 (23 in error). A large, elongate pygidium. 



Upper Helderberg limestone. Williamsville, Erie county. 

 Fi^ r . 29. An unusually huge pygidium. 



Upper Helderberg limestone. Williamsville, Erie county. 

 Kii. r . 30. Profile view of the pygidium represented in tig. 28. 

 Fig. 31. Profile view of the pygidium represented in fig. 29. 



Proetus (?) lonoicaudus. 



Page 131. 

 Fig, 32. Anterior aspect of the type specimen. 

 Pig. :;:',. Profile view of the same. 



Fig. 42. Posterior aspect of the same. 



Hamilton group ! Locality doubtfidi from Somi point uurlli-uist of Des Moines, Towa, 



[Probably of Lower Carboniferous age.] 



