VERTEBRATES. 393 



Genus AttTLIODUS, ¥. and W. 



Antliodus perovalis, St. J. and W. 



PL XI, Kg. S3. 



Teeth small, very compressed, nearly circular in outline viewed from 

 the concave aspect, broadly and strongly arched along the crest. Con- 

 cave crown-face moderately depressed, basal line probably well-defined 

 from the root, broadly arched downward, forming an obtuse angle at 

 the lateral extremities ; the convex face is much lower than the opposite 

 face, nearly plane vertically and gently arched laterally, slightly pro- 

 duced outward forming an obtuse angle along the basal margin with 

 the basal area below, and bordered by a rather wide coronal fold which 

 spans the crown in a nearly direct course. The surface is smooth, or 

 striato-punctate along the crest especially in the convex face. Lateral 

 dia'meter of tooth .14 inch, bight of convex crown-face .06, bight of con- 

 cave face about .15. 



Of the present form only a single specimen is known to us, and this 

 is imperfect in the basal region. The root was probably very small, and 

 the concave crown-face was bordered by a coronal belt, of which only a 

 faint trace is visible in the specimen. The tooth is somewhat like A. 

 sarcululus of the Upper Burlington limestone, but it is readily distin- 

 guished by its circular outline and laterally worn strongly arched con- 

 vex crown-face. 



The original, which belonged to the collection of Prof. Worthen, 

 was lost at the time of the fire in the building occupied by the State 

 Geological Museum, in Springfield, February, 1871. 



Position and locality : Warsaw beds ; Warsaw, Illinois. 



Antliodus gracilis, St. J. and W. 



PI. XI, Fig. 29. 



Teeth small, oval in outline. Crown moderately compressed, crest 

 regularly arched and sharp, presenting a striato-punctate structure in 

 worn surfaces; convex face irregularly elliptical in outline, but slightly 

 arched in either direction, basal line nearly horizontal in the median 

 region, but towards the extremities suddenly and gracefully curved 

 upwards forming obtuse angles about one-fourth the distance from either 

 extremity, coronal fold narrow and apparently simple ; concave side 

 broadly elliptical in outline, moderately depressed in the longest diame- 

 ter, and curved backward at the lateral borders, basal line probably 

 nearly corresponding to the outline of the crest, but in the specimen 



—51 



