Plate II. 



All specimens represented four-fifths natural size unless otherwise stated. 



Fig. 1. Dipterus calvini Eastm. Cedar Valley limestone 

 (Middle Devonian) ; Fairport, Iowa. Right mandibular plate, 

 liolotype of the species. Page 219 



Fig. 2. Dipterus pectinatus, sp. nov. State Quarry beds (Up- 

 per Devonian) ; North Liberty, Johnson county, Iowa. Left 

 mandibular plate, cotype. A photograph of the same specimen 

 is reproduced in Plate VII, fig. 13. Page 222 



Fig. 3, 3a. Dipterus uddeni Eastm. Base of Cedar Valley 

 limestone (Middle Devonian) ; Buffalo, Iowa. Left man- 

 dibular plate of liolotype, shown from the oral and lateral as- 

 pects. Page 218 



Fig. 4. Dipterus mordax Eastm. State Quarry beds (Up- 

 per Devonian) ; North Liberty, Johnson county, Iowa. Eight 

 mandibular dental plate ; contour not entirely complete. Cotype. 

 Page 220 



Fig. 5. Dipterus mordax Eastm. A worn and somewhat 

 fragmentary specimen from same horizon and locality as the last. 

 Cotype. Page 220 



Fig. 6. Dipterus digitatus, sp. nov. Left palatal dental plate 

 of cotype from same locality and horizon as the preceding. A 

 photograph of the same specimen is reproduced in Plate VII, 

 fig. 20. Page 221 



Fig. 7. Dipterus pectinatus, sp. nov. Palatal dental plate 

 of cotype from same horizon and locality as the preceding. The 

 concavity of the oral surface is in reality greater than the artist 

 has here represented, and the lower right-hand margin is 

 slightly deficient in the original. Other specimens illustrating 

 the upper dentition of the same species are shown in Plate VII, 

 figs. 11, 12 and 15. Page 222 



Fig. 8. Dipterus costatus Eastm. Left mandibular dental 

 phite selected as liolotype of the species, from same horizon and 

 locality as the preceding. Page 220 



298 



