354 PALAEONTOLOGY OF ILLINOIS. 



GENUS CLADODUS. 

 CLADODUS ISCHYPUS, N. and W. 



PL iv, fig. 6, 6a. 



TEETH large and stong; base broad and thick, one and a 

 half inch wide by five-eighths of an inch in its antero-pos- 

 terior diameter ; central cone three-quarters of an inch in 

 hight, broad and thick below, rapidly narrowed to an acute 

 point (in the specimen before us the summit is deflected for- 

 ward and laterally) ; anterior face nearly flat, posterior 

 strongly arched, both finely striated, forming an acute angle 

 along their line of junction ; lateral denticles numerous, in a 

 single row on the anterior margin, and running up on to the 

 lateral angle of the crown. 



The most striking characters of this tooth are its broad thick base in its 

 longest diameter double the hight of the crown and the strong, anteriorly 

 flattened and rapidly tapering central cone. These characters, if equally 

 marked in other specimens, will serve to distinguish it at a glance from any 

 other species hitherto described. 



Specimen in cabinet of Prof. Litton. 



Formation and locality : St. Louis limestone ; St. Louis, Mo. 



CLADODUS ELEGANS, N. and W. 



PL iv, fig. 9. 



TEETH of medium size, as high as broad, measuring about 

 one inch in each direction ; central cone very much compressed, 

 double-edged ; anterior face nearly flat, posterior gently arched 

 and regularly striated with nearly equidistant, relatively 

 strong and sharp raised lines, at base about thirty in number, 

 above fewer and stronger ; lateral denticles two on either side, 

 of which the exterior pair is much the larger, divergent, flat- 

 tened before, rounded behind, double-edged, strongly striated. 



The general contour of this tooth is remarkably exact and elegant, as is its 

 ornamentation. The central cone is erect, straight and very much flattened. 



