264 PALEONTOLOGY OF ILLINOIS. 



compressed and deeply denticulate crest, the intermediate denticles 

 irregularly alternating in size; tbe exterior pair in the normal state 

 are remarkably large, more strongly compressed in front than behind, 

 with sharp cutting edges, the apices almost always directed toward 

 the median cone ; in many instances, the larger exterior pair are flanked 

 by a second pair of denticles with a minute intervening cusp ; and all 

 are ornamented in the outer face by more or less strongly marked 

 carinas, which are either simple or give off spinose processes towards 

 their bases, which latter are more strongly developed in the lateral 

 than in the median portions of the crown ; the median cusp is strong, 

 trenchant, sigmoidally curved and laterally deflected, compressed in 

 front and broadly rounded behind, with a slight depression occupying 

 the basal portion in front; the carinas are more strongly developed in 

 front than in the opposite face, though their development is very 

 irregular, as shown iu a large suite of specimens — in some individuals 

 there being very few and these scarcely reaching one-third the distance 

 towards the apex, while in others they show several sharp, close set 

 costse implanted and bifurcated in their descent ; the carina? are rela- 

 tively coarser and far less numerous in the lateral denticles, though 

 always irregularly disposed ; the inner face of the crown exhibits simi- 

 lar variableness in the development of the costas, though relatively cor- 

 responding to their development in the opposite face ; in some examples 

 the inner face of the principal cone is quite smooth, with only faint 

 costse visible in the lateral portions; in others, again, the costae are 

 quite numerous, but in all cases they are less strong than iu the outer 

 face; the carinas are sharp, the intervening space presenting a slight 

 and regularly concave channel when they are crowded ; in the principal 

 cone they are terminated before reaching the lateral edges in front, and 

 the same is true of the posterior face — the lateral costas being shortest 

 and soonest becoming obsolete. Large individuals exceed an inch in 

 greatest lateral diameter of base and one-fourth to one-third greater 

 than the entire hight of the tooth. 



The score and a half or more of individuals to which I have had 

 access, through the kindness of Mr. Wachsmxttb, in drawing up the 

 foregoing description of this interesting and beautiful species, present 

 a range in size from teeth of . 2 inch in lateral diameter to those mea- 

 suring nearly one inch in the same direction ; and otherwise exhibiting 

 considerable diversity in the details, especially the superficial ornament- 

 ation. These latter may be best represented in the illustrations which 

 have been introduced. 



Position and locality : Authentic examples of the species have thus 

 far been observed only in the upper fish-bed of the Kinderhook, at Bur- 

 lington, Iowa, where Mr. TYachsmttth, to whom we have dedicated 

 the species, has obtained a beautiful series of specimens. 



