274 PAL2E0NT0L0GY OP ILLINOIS. 



apex, laterally deflected, rather strongly recurved, gently arched in 

 front, strongly convex posteriorly, with compressed, sharp cutting 

 edges; lateral denticles one on either side, relatively strong, divergent, 

 similar in form and recurvation to the principal cone, with which they 

 are connected by a low, sharp coronal crest ; the anterior face is marked 

 with a few short, sharp-crested, widely spaced costre, which are appar- 

 ently confined to the basal region, the greater extent of the cusps being 

 smooth, and beautifully polished, as also the posterior face, with the 

 exception of a faint carina in the angle between the cones, and which 

 may terminate in a delicate rudimentary denticle. A medium-sized 

 specimen measures 1.25 inches in lateral diameter of base, and about 

 equal to the greatest bight of the tooth, antero-posterior diameter .45 

 to .50, liight of median cone 1 inch, hight of lateral denticles about .55 

 inch. 



The recognition of the present form is based upon a few specimens 

 discovered by Mr. Tan Horne, one of which presents a nearly perfect 

 tooth of medium size. Another consists of the base of a remarkably 

 large individual, measuring in greatest diameter 1.80 inches, postero- 

 anterior diameter .75, and agreeing intimately with the lesser specimen 

 in form and contour. Others exhibit worn and fragmentary examples 

 of smaller teeth. The peculiarities possessed by these teeth readily 

 distinguish them from other forms of the genus, and, with the excep- 

 tion of a single specimen in the collection of Mr. Springer from the 

 upper Burlington limestone, which has been provisionally referred to a 

 distinct species, under the name of C. prwnuntius, it has no intimate 

 ally. It is one of the largest and most interesting species as yet made 

 known, and must have belonged to fishes of truly formidable size, and 

 we have a commensurate pleasure in dedicating the species to its dis- 

 coverer. 



Position and locality : Bare in the upper beds of the St. Louis lime- 

 stone ; Alton, Illinois. 



Cladodxjs etjglypheus, St. J. and W. 



PI. IV, Fig. 1-3. 



Teeth minute, or attaining a size below the medium. Base denned 

 in front by a broad, moderately deep sinuatiou, extending betweeu the 

 angles produced by the anteroinferior bosses, thence retreating to the 

 lateral extremities, which are produced and sharply rounded to the 

 broadly curved posterior margin; moderately excavated below, a faint 

 marginal rim between the anteroinferior bosses, and faintly beveled 

 behind ; postero-superior surface gently arched and occupied by a pair 

 of rather prominent protuberances or bosses, which are separated by a 



