PLATE XVI b. 



ACIDASPIS CALLICERA. 

 Page 89. 

 Fig'. 1. An imperfect specimen, natural size, retaining the head and six thoracic segments. 

 Fig. '_'. The same, enlarged to two diameters. 



Corniferous limestone. Camillus, Onondaga county. 

 Fig. 3. A larger, more nearly entire individual, drawn to two diameters. The specimen is an internal 



cast in decomposed chert, and has the cephalon somewhat deflected. 

 Fig. 4. Profile of the same, similarly enlarged. 



Fig. 5. An anterior view of the same, showing the elevation of the glabella and eye-lobes. 

 Fig. 6. The natural mould of the dorsal surface of the same specimen, similarly enlarged. 

 Fig. 7. A gutta-percha impression from this mould, showing the ornamentation of the surface. 



Upper Helderberg limestone. Cayuga, Province of Ontario. 

 Fig. 8. The glabellar portion of a small cephalon, enlarged to two diameters. 



Upper Helderberg limestone. Cayuga. Province of Ontario. 

 Fig. 9. The left movable cheek, showing the length of the marginal and genal spines. Enlarged to four 

 diameters. 



Corniferous limestone. Canandaig ita, Ontario county. 

 Fig. 10. The glabellar portion of a head, enlarged to two diameters, showing the denticulations on the 

 frontal margin. 



Upper Helderberg limestone. Cayuga, Province of Ontario. 

 Figs. 11 and 12. Right and left movable cheeks, drawn from internal casts, and showing the number of 

 marginal spines. 



Upper Helderberg limestone. Cayuga, Province of Ontario. 

 Fig. 13. Lateral view of a left movable, cheek, retaining the eye. Enlarged to two diameters. 

 Schoharie grit. Near Clarksville, Albany county. 



ACIDASPIS, Sp. 



Page 71. 



Fig. 14. An imperfect pygidium, enlarged to two diameters. 



Upper Helderberg limestone. Cayuga, Province of Ontario. 



ACIDASPIS ROMINGEKI. 



Page 71. 



Fig. 15. A fragmentary pygidium, restored in outline to show the great length of the marginal spines. 



Enlarged to two diameters. 

 Fig. 16. The same in profile. 

 Fig. 17. A portion of the anterior marginal spine of the same specimen, to show the character of the 



ornamentation. Enlarged to six diameters. 

 Fig. 18. A similar enlargement of the terminal portion of the fourth marginal spine. 

 Hamilton group. Little Traverse Bay, Michigan. 



