PLATE 73. 



Piige 



Fig. 1-4. Bronteus barrandi. 350 



1 . The pygUlium of the natural size. ( The specimen is impi'rfect. and the figure is completed 



from a cast of the impression in stone.) 



2. Tlie impression of the same. 



3. Profile of the same. 



4. Jlnlargemcnt of the surface, showing the undulating stria^ and minute granulations. 



Fig. 5-7. Proetus protcberans. 351 



5. The head of this species. 



fi. A fragment preserving the head and part of the thora.x. 



f) a. Lateral view of the same. 



7. The pygidium of another individual. 



7 a. Profile of the same. 



Fig. 9 - 13. Homalonotus vanuxemi. 852 



9. A fragment of the thorax of a specimen of medium size. 



10. The pygidium of a small sjjecimcn. 



11. Profile view of the same. 



12. The pygidium of a large individual. 

 I'i. An enlargement of the surface. 



Note. The differences in the two specimens of the pygidium here figured induce a doubt of their specific 

 identity -. the distinctly trilobate character of the smaller specimen contrasts strongly with tlie larger one, 

 in which the lobes and annulations are less distinctly marked, while the extremity has been much more ex- 

 tended. The smaller form may be regarded as the typical form of H. vanvxemi ; while the larger one may 

 perhaps prove a distinct species, or at least a strongly marked variety. 



The fragment of the thorax figured is very much flattened upon the back; and though its relations are 

 not determinable, it appears more nearly related to the smaller than to the larger pygidium. It will require 

 better materials for the satisfactory determination of these species. 



Fig. 15 - 25. Phacops looani. 863 



15. An entire specimen which has the head compressed from above, and the eyes a little 



distorted. 



16. View of a specimen which is enrolled. 



17. The head of a larger individual which shows the transverse furrows, and preserves the 



eyes in their proper form. 



18. A larger head, which has few pustules in the space between the eye and the dorsal furrow. 



19. Front view of fig. 17. 



21. View of the lower side of the head of another specimen, showing some crenulations along 



the marginal furrow. 



22. The lower side of a specimen in which the granulation is worn from the surface of the 



glabella, and showing the line of the hypostomal suture. 



23. The eye enlarged. 



24. A portion of the eye, from which the lenses have been removed by weathering. 

 24 a. An enlargement of a portion of the eye. 



25. The hypostoma. 



Fig. 26, 27, 28. Phacops hudsonicds. 365 



20. The head of this species. 27. Profile of the same. 28. The eye enlarged. 



Correction for description on page 3.55. IIcad semielliptieal : length greater than half the width; 

 posterior angles extended and abruptly rounded. Cheeks broad triangular, produced behind. 



