EXPLANATION OF PLATE XVI. 



Figures 1-3 ILLAENUS HARRISI n. sp p. 218 



Anterior, dorsal and lateral views of the type specimen, from 

 Bridgeport. (Pal. Coll. Walker Museum, No. 8,613. Collect- 

 ed by G. F. Harris). 



Figures 4-6 ILLAENUS GRAFTONENSIS M. & W p. 223 



Dorsal, anterior and lateral views of a nearly perfect cephalon 

 from Joliet. (Pal. Coll. Walker Museum, No. 6.855, Gurley 



Collection.) 







Figures 7-9 ILLAENUS TRANSVERSALIS n. sp p. 224 



Anterior, dorsal and lateral views of the type specimen, the 

 lateral and anterior views restored in part, from Bridgeport. 

 (Pal. Coll. Walker Museum, No. 8,614. Collected by G. F. 

 Harris.) 



Figures 10-12 ILLAENUS CHICAGOENSIS n. sp p. 220 



Anterior, dorsal and lateral views of the type specimen, from 

 Hawthorn. (Pal. Coll. Walker Museum, No. 9,910, Van 

 Home Collection.) 



Figures 13-16 ILLAENUS IMPERATOR Hall p. 225 



13-15, Dorsal, anterior and lateral views of an incomplete small 

 cranidium. 16, Dorsal view of a pygidium. Both spec- 

 imens from Joliet. (Pal. Coll. Walker Museum, No. 10,728, 

 Van Home Collection.) 



