EXPLANATION OF PLATES. 20 7 



PLATE XI. 



DiKELOCEPHALUS MINNESOTENSIS. /j8 



Fig. 1. The hypostoma of this species. 

 «« 3. A cheek of the same. 

 «< 4. A pygidium of the same. 



Fia. 2. A cheek of D. pepinensis? 



Fig. 5 & G. Spines of an undetermined trilobite, referred by Dr. D. D. Owen to 

 Lonchocephalus hamulus. 



Aglaspis barrandi. 



Fig. 7. A large carapace of this species. 



<» 8. A smaller carapace. 



«« 9. The lower side of a part of a small carapace, showing the cavities of the eyes. 



«* 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. 



«< 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. 



