VERTEBRATES. 45 



Antliodus sulcatus, N. and W. 



PI. Ill, Fig. 5, 5 a. 



Teeth of medium size, broad, thin, flattened, with an ellip- 

 tical outline; posterior face long, elliptical, smooth, less than 

 half as high as broad, slightly concave vertically, laterally 

 straight, superior margin regularly arched, truncated, and 

 slightly sulcated, sulcus about one-sixth the height of the face, 

 its posterior margin lowest, both margins porous and roughened 

 by the terminations of the vertical enamel tubes ; coronal ridge 

 regularly curved downward, narrow, not prominent, showing 

 about three imbricating folds ; posterior face broader than ante- 

 rior, elliptical in outline, very slightly arched vertically and 

 horizontally, rough ; coronal ridge wanting ; base narrow and 

 roughened with the rudimentary root. 



Much like the preceding species in general aspect but broader, thinner and 

 more distinctly sulcate; anterior face more flattened. 



Figures 5, 5 a, represent the posterior face and section, natural size. 

 Formation and locality: Keokuk limestone, Warsaw, Illinois. 



Genus DACTYLODUS, N. and W. 

 Dactylodus princeps, N. and W. 



PL III, Figs. 6, 6 «, 6 6. 



Teeth large and robust, slightly higher than broad ; superior 

 border of crown regularly arched, obtuse and porous ; anterior 

 face three-tenths of the height of the tooth, sloped downward 

 at an angle of about 30°, to an obtuse transverse ridge, surface 

 smooth and gentry arched horizontally ; posterior face imper- 

 fectly elliptical, nearly flat, smooth, in weathered specimens 

 more or less porous, about twice as high as the anterior face, 

 bounded below by a thick coronal ridge, obscurely marked with 

 imbricating folds. This ridge is somewhat bow-shaped, termi- 



