Plate II. — Continued. 



Fig. 9. Dipterus nelsoni Newberry. Chemung beds; War- 

 ren, Pennsylvania. Oral surface of greatly abraded dental plate, 

 worn so as to simulate the smooth forms usually referred to 

 Sagenodus. Page 223 



Fig. 10. Dipterus murchisoni Pander. Middle Devonian; 

 Berndorf, Eifel District. Eight mandibular dental plate of a 

 Eussian and Eifelian species approximating closely to the D. 

 mordax series of Dakotan seas (cf. Plate VII, figs. 5-9). Orig- 

 inal in Museum of Comparative Zoology. Page 226 



Figs. 11, lie. Dipterus nelsoni Newberry. Chemung beds; 

 Warren, Pennsylvania. Eight mandibular dental plate shown 

 from the antero-lateral and oral aspects. The same specimen 

 is shown in natural juxtaposition with its fellow of the left side 

 in Plate VII, fig. 3. Page 223 



Figs. 12, 12a. Small dermal tubercle, supposed to be of 

 Chimaeroid nature, from the Kinderhook limestone of Burling- 

 ton, Iowa. Compare with Fig. 15. Page 149 



Figs. 13, 14. Thelodus-like scales from the Columbus lime- 

 stone (Middle Devonian) of Columbus, Ohio, x 3-1. Page. . .72 



Figs. 15, 15a. Large-sized Chimaeroid (!) dermal plate from 

 the Kinderhook limestone of Burlington, Iowa. Page 149 



Fig. 16. Dipterus fleischeri Newberry. Oneonta beds ; Frank- 

 lin, Delaware county, New York. Eight palatal dental plate. 

 Page 225 



Fig. 17. Dipterus sp. ind. Worn example of palatal dental 

 plate from the State Quarry beds (Upper Devonian) of John- 

 son county, Iowa. Page 216 



Fig. 18. Scale-like dermal plate supposed to be of Chimae- 

 roid nature, and theoretically associated with Ehynchodus. 

 Compare with the young example of Acanthaspis armata 

 shown in Plate I, fig. 14, and with the so-called "shoulder- 

 girdle of Ehamphodus" as described by 0. Jaekel. Hydraulic 

 limestone (Hamilton); Milwaukee, Wisconsin. Page 126 



Fig. 19. Synthetodus calvini, sp. nov. State Quarry beds 

 (Upper Devonian) ; North Liberty, Johnson county, Iowa. 

 Holotype. Original in Museum of Comparative Zoology, Cam- 

 bridge, Mass. Page 233 



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