PLATE XXIII. 



PAGE. 



CTENACANTHUS HABBISONI. St. J. and W 23fi 



Fig. 1 a. View of right side of spine, outline partially restored; 1 b, do., from the 

 dorsal edge; 1 c, do., posterior face; 1 d, e, f, sections at broken distal 

 end, at opening of pulp cavity, and the inferior dorsal angle. St. Louis; 

 Alton, Mr. St. John. 



EUNEMACANTHUS cosTATUs, (N. and W. sp.) 246 



Pig. 2 a. Side view of spine, somewhat distorted, and showing in conseauence nearly 

 the entire breadth of the dorsal ridge towards the base; 2 b, do., view of 

 the dorsal angle; 2 c, do., showing posterior face, with the lateral walls 

 crushed together below; 2 d, do., transverse sections just below middle 

 and near tip. St. Louis limestone; Alton, 111., Mr. Butters. 



