PLATE 4 



Dipterus calvini Eastm. 



Page i6o 



Right mandibular plate. Natural size 



Cedar Valley limestone (Middle Devonic) ; Fairport, la. 



Original in Museum of Comparative Zoology, Cambridge, Mass. 



Dipterus sp. nov. 



Page 164 



Left mandibular dental plate. Natural size 



State Quarry beds (Upper Devonic) ; Nort!i Liberty, Johnson co., la. 



Original in Museum of Comparative Zoology, Cambridge, Mass. 



Dipterus uddeni Eastm. 



Page 160 



Left mandibular dental plate. Natural size 



Base of Cedar Valley limestone (Middle Devonic) ; New Buffalo, la. 

 Original in Museum of Comparative Zoology, Cambridge, Mass. 

 Lateral aspect of same specimen as shown in figure 3 



Dipterus mordax Eastm. 



Page 161 



Right mandibular dental plate. Natural size 



State Quarry beds (Upper Devonic) ; North Liberty, Johnson co., la. 



Original in Museum of Comparative Zoology, Cambridge, Mass. 



A worn specimen from same horizon and locality as the last. Natural 



size 



Dipterus sp. nov. 



Page 164 



Palatal dental plate of undescribed species. Natural size. The func- 

 tional surface is in reality more concave than is here represented. 

 From same horizon and locality as the original of figure 5 



Dipterus sp. nov. 



Page 164 



Palatal dental plate of undescribed Dipterine species. Natural size 

 State Quarry beds (Upper Devonic) ; North Liberty, Johnson co., la. 

 Original in Museum of Comparative Zoology, Cambridge, Mass. 



