28 PALAEONTOLOGY OF ILLINOIS. 



the denticles; principal cone conical in outline, compressed, 

 aneipital, anterior surface marked with about 6 (3 on either 

 side of the centre) smooth, longitudinal costse, or sharp, coarse, 

 prominent strice, which converge at the base of the cone ; 

 lateral denticles two on either side, conical, compressed, and 

 marked like the middle cusp, with a few prominent longitudi- 

 nal carinoe. 



This is a remarkably neat little species, clearly distinct from any with which 

 it is associated, or that have been heretofore described. It is related, however, 

 to C. Hibberti, Ag., from the limestone of Burdie House, but in that species 

 the lateral cusps are much more unequal in size, and, like the principal cone, 

 are finely and evenly striated from base to summit. 



There is another small, compressed, sparsely striated species in the collec- 

 tion, from the Coal Measures of Indiana (C. gracilis, Nob.), but in that the 

 central cusp, though compressed,, is narrower, and the lateral ones are long, 

 curved and cylindrical. 



Figure 13, 13 a, anterior face and base, natural size. 



Formation and location: Chester limestone, Chester, Illinois. 



Cladodlts turritus, N. and W. 



PL 1, Fig. 14. 



Teeth of medium size, higher than long; base thin, flat, 

 shorter, laterally, than the height of the median cone, sub- 

 elliptical in outline, wider behind than before; median cone 

 conical, covering more than half the base, sigmoidally curved, 

 the point turned forward, compressed, with cutting edges, 

 anterior and posterior faces unequally arched, and often flat- 

 tened along the median line, producing an angular section, 

 both faces finely striated, striation of posterior surface strongest; 

 lateral denticles one on either side, with a rudimentary tubucle 

 between it and the principal cone, nearly vertical, compressed, 

 acute, striated, and curved in the same way as the median cone. 



The typical form of this species, represented by Fig. 14, in the narrow, con- 

 ical and rigid outline of the central and lateral cusps, resembles a miniature 



