30 PALAEONTOLOGY OF ILLINOIS. 



cipal cone is much less compressed, is more strongly and generally striated and 

 the strias are of very different character. In G. grandis they are fine, acute 

 and often broken and forked, while in C. magnijicus they are stronger, flattened, 

 nearly continuous and parallel. The lateral denticles, too, in G. magnificus are 

 nearly smooth, while in G. grandis they are rendered angular by the strong 

 though few striaj, which they bear. 



Fig. 15 represents the anterior face of a nearly perfect tooth; 15a, a perfect 

 base of a smaller specimen — both of the natural size. 



Formation and locality: Chester limestone, Chester, Illinois. 



Cladodus Lamnoides, N. and W. 



PI. I, Figs. 16, 16ff. 



Teeth small, height exceeding length of base; base narrow, 

 straight before, arched behind, relatively thin, smooth; median 

 cone narrow, conical, recurved or often doubly curved, slightly 

 rounded before, strongly so behind, very acute at point, with 

 cutting edges which extend to near the base; anterior surface 

 smooth; posterior face finely striated longitudinally, except 

 near the point, which is smooth; lateral denticles two, one- 

 fourth the length of the principal cone, sub-cylindrical, acute. 



This is a remarkably neat and graceful species; in form not unlike the teeth 

 of some of the living species of Lamna. When showing only the anterior sur- 

 face of the tooth, it might be mistaken for G. politus; but in that species the 

 base is broader, the lateral denticles are double on either side, and are not set 

 on the margin of the base. 



Fig. 16 represents the posterior surface, with a section of the median cone; 

 Fig. 16 a is a side view of same tooth — both natural size. 



Formation and locality: Keokuk limestone, Warsaw and Nauvoo, Illinois. 



Cladodus gracilis, N. and W. 



PL I, Fig. 17. • 



Teeth small, delicate and slender in all parts, height about 

 equal to breadth; median cone narrowly conical in outline, 



