Explanation of the Plates. 



337 



PLATE VI. 



DlKELOCEPHALTJS MINNESOTENSIS. 



Fig. 1. The Hypostoma of this species. 

 w 3. A cheek of the same. 

 " 4. A pygidium of the same. 



" 2. A cheek of D. pepinensis ? 



" 5 & 6. Spines of.au undetermined irilobite. referred by Dr. T>. D. Owex to Lmrhocephalu* 

 hamulus. 



Aglaspis barrandi. 



Fig. 7. A large carapace of this species. 

 M 8. A smaller carapace, which is broken and distorted. 



" 9. The lower surface of a part of a small carapace, showing the cavities of the eyes. 

 14 10. Enlargement of the surface. 



" 11. A portion of the crust, which may have been of a segment at the posterior part of the 

 body. 



11 12, 13, 14. Fragments which appear to be the extremities of thoracic segments. 

 " 15, 16. Spines corresponding in character to the crust in other parts of the body; probably 

 caudal spines. 



