EXPLANATION OF PLATES. 203 



TLATE IX. 



DiKELOCEPHALUS PEPINENSIS. 



Fig. 1. Glabella and fixed cheeks. The anterior furrows are scarcely shown in the 

 figures. 

 «' 2. Pj'gidium of the same species. 

 «* 3. A cheek. 

 << 4. Ilypostoma of the same. 



DiKELOCEPHALUS MINNESOTENSIS. / -^ o 



Fig. 5. Glabella and fixed cheeks. The frontal limb is represented in outline, from 

 another specimen in which this part is preserved. From Mazomania. 



'« 0. A small pygidium from Lagrange mountain. 



" 7. A large pygidium from the Magnesian limestone near Madison, Wisconsin. 



«' 8. A thoracic segment; one side restored in outline. 



<< 9. Part of a small hypostoma, 



<« 10. Part of a la,rger hypostoma. 



DiKELOCEPHALUS MINNESOTENSIS, Var. 

 Fig. 11. Glabella, fixed cheeks, and frontal limb. 



DiKELOCEPHALUS MINNESOTENSIS, Var. LIMBATUS. /^ / 

 Fig. 12. A part of the glabella and frontal limb of this variety. ,^ f^Ht'^ t\ 



Triarthrella auroralis. 



Fig. 13. Glabella and fixed cheeks, twice enlarged From Lagrange mountain. 



