Plate I. 



Fig. 1. Diplodus striatus Eastm. Upper Devonian ; Elm- 

 hurst, Illinois. Detached tooth, anterior face, x 4-1. Page 1C5 



Fig. 2. Detached dorso-median plate of a small undetermined 

 Arthrodire seen from the visceral aspect. Hydraulic limestone 

 (Hamilton) ; Milwaukee, Wisconsin, x 2-1. Page 207 



Fig. 3. Onychodus hopkinsi Newberry. Chemung beds; 

 Franklin, Delaware county, New York. Series of five presym- 

 physial teeth, x 3-4. Page 241 



Fig. 4. Onychodus sp. (cf. 0. sigmoides Newb.). Hydraulic 

 limestone (Hamilton) ; Milwaukee, Wisconsin. Imperfect slight- 

 ly arcuate presymphysial tooth seen partly in longitudinal sec- 

 tion and displaying central pulp-cavity, x 2-1. Page 240 



Fig. 5. Diplodus priscus Eastm. Upper Devonian ; Elmhurst, 

 Illinois. Detached tooth, anterior face, x 4-1. Page 104 



Fig. 6. Detached dorso-median plate comparable to that 

 shown in Fig. 2, and belonging to an unknown Arthrodiran 

 genus. Hydraulic limestone (Hamilton) ; Milwaukee, Wisconsin, 

 x 2-1. Page 207 



Figs. 7, 8. Detached Thelodus-like scales from the "bone- 

 bed" of the Columbus limestone, near Columbus, Ohio, x 3-1. 

 Page 72 



Fig. 9. Phoehodns politus Newberry. Cleveland shale (Up- 

 per Devonian) ; Lorain county, Ohio. Detached tooth, anterior 

 face, x 4-1. Page 1 06 



Fig. 10. Dinichthys pustulosus Eastm. Hydraulic limestone 

 (Hamilton) ; Milwaukee, Wisconsin. Left posterior palato- 

 pterygoid dental plate or "shear-tooth." x 1-1. Page 194 



Fig. 11. Onychodus sp. (cf. O. sigmoides Newberry). Mar- 

 cellus shale (Erian division of the Middle Devonian) ; Oran, 

 Onondaga county. New York, x 1-1. Page 241 



294 



