PLATE XXVI. 



PAGE. 



ACONDYLACANTHUS? xiPHiAs, St. J. and W 244 



Fig. 1 a. View of right side of spine, the extremities and posterior border restored in 

 outline; 1 b, do., transverse section near middle posterior face restored in 

 outline. Keokuk; Keokuk, Iowa. Mr. Cox. 



ACONDYLACANTHUS EECTUS, St. J. and W, 241 



Fig. 2, a. View of spine from right side; 2 b, do., section of posterior face enlarged; 2 c. 

 do., enlargement from middle of spine. Upper Coal Measures; LaSalle, 111. 

 Prof. Worthen.. 



ACONDYLACANTHUS NUPEKUS, St. J. and W 242 



Fig. 3, a. View of spine from left side; 3 b, do., enlargement above middle of spine; 3 c, 

 do., transverse section. Upper Coal Measures; Peru, 111.. Mr. Tiffany. 



GYKACANTHUS? COBDATUS. St. J. and W 251 



Fig. 4 a. View of spine from the anterior edge, outline restored; 4 b, do., from the pos- 

 terior face; 4 c, do., from the right side; 4 d, do., left side; 4 e, do., transverse 

 sections at different parts of the spine, the posterior wall destroyed at both 

 extremities, as shown in figure 4 b. Keokuk; Keokuk, Iowa. Mr. Cox. 



