EXPLANATION OF PLATE XX. 



^Figure 1 BRONTEUS ACAMAS Hall p. 232 



Dorsal view of a nearly complete pygidium, from Romeo. (Pal. 

 Coll. Walker Museum, No. 10,733. Collected by J. H. Ferris.) 



Figure 2 HARPES TELLERI n. sp p. 213 



Dorsal view of the type specimen, a nearly complete cranidium, 

 from Milwaukee, Wis. (Collection of Mr. E. E. Teller plasto- 

 type, Pal. Coll. Walker Museum, No. 10,734.) 



Figures 3-5 CYPHASPIS INTERMEDIA n. sp p. 231 



3, Dorsal view of an incomplete cranidium with the free cheeks 

 restored in outline. 45, Dorsal view of another cranidium 

 with the profile in outline. Both specimens from near 

 Channahon, Will Co., 111. (Pal. Coll. Walker Museum, No. 

 10,735.) 



Pigures 6-7. PROETUS CHANNAHONENSIS n. sp p. 228 



6, Dorsal view of a nearly complete cephalon. 7, Dorsal view 

 of a pygidium. Both specimens from near Channahon, 

 Will Co., 111. (Pal. Coll. Walker Museum, No. 10,736.) 



Figures 8-9 PROETUS? HANDWERKI n. sp p. 229 



Dorsal -and lateral views of the type specimen from near 

 Lemont. (Pal. Coll. Walker Museum, No. 9,911. Collected 

 by J. H. Handwerk.) 



Pigures 10-12 ARCTINURUS OCCIDENTALIS Hall .....p. 247 



10, Dorsal view of an incomplete pygidium, from Bonfield, 

 111. (Pal. Coll. Walker Museum, No. 6,867, Gurley Col- 

 lection.) 11, Dorsal view of another incomplete pygidium, 

 from Joliet. (Pal. Coll. Walker Museum, No. 10,738, Van 

 Home Collection.) 12, Fragment of the anterior portion of 

 a cephalon which may belong to this species, from near 

 Lemont. (Pal. Coll. Walker Museum, No. 10,739.) 



