Plate IV. 



Dinichthys pustulosus Eastm. Lower part of the Cedar Val- 

 ley limestone (Middle Devonian) ; near Rock Island, Illinois. 

 Dorsal aspect of moderate-sized headshield, showing cranial 

 sutures, sensory canals and other features very distinctly. The 

 median occipital plate is removable, showing conformation of 

 the visceral surface, and median depression for the attachment 

 of muscles, etc. Original collected by Mr. A. S. Tiffany, of 

 Davenport, and now preserved in the Museum of Comparative 

 Zoology, Cambridge, x 1-2. Page 194 



308 



