TRILOBITA—PROPARIA. 3 1 7 



159. H. delphinocephalus (Green). (Fig. 1630.) Siluric. 



Dorsal shield convex; cephalon depressed in front. Pygidium 

 strongly triangular, acute, with 12 annulations. Entire surface 

 granulose. 



Niagaran of New York and Ontario to Indiana. 



Fig. 1630. Homalonotus delphinocephalus, y^ ^. (After Hall.) 



160. H. vanuxemi Hall. • Devonic. 



Like H. delphinocephalus in form but differs in the pygidial 



axis having 9 or 10 annulations instead of 12, and in the anterior 



