VERTEBRATES. 87 



difference of color, with the variety and beauty of its ornamentation, fully jus- 

 tify us in the choice of the name given it. There is no described species with 

 which it is likely to be confounded. 



Figures 18, 18a, 18b, represent the tooth viewed from behind and above, 

 and a profile section, and are of the natural size. 



Formation and locality: Keokuk limestone, Keokuk, Iowa. 



Helodus consolidatus, N. and W. 



PI. VI, Figs. 1, la, 2, la. 



Tooth compound, consisting of several crowns, firmly consoli- 

 dated upon a common root ; these crowns diverge at different 

 angles from a common centre, and are very unequal in size; 

 anterior and larger one broadly conical in profile, both laterally 

 and transversely, irregularly oblong in outline, ends somewhat 

 rounded; second crown much smaller, conical in profile, with 

 a more or less prominent central gibbosity, oblong-linear in 

 outline, ends rounded ; third crown smaller than the second, 

 arched in profile, elliptical in outline, sometimes rudimentary 

 and even wanting. Root nearly as broad as the principal 

 crown, vermicularly rugose above, roughened and bony below, 

 with two marked excavations beneath the larger crowns; pos- 

 terior margin forming a blunt edge, somewhat rounded laterally. 

 The enameled surface of all the crowns uniformly, somewhat 

 finely punctate, sometimes showing a tubercular rugosity. 



There is little doubt that these teeth formed one or more medial series be- 

 tween the broader lateral teeth of CocMiodus. With what species of that genus 

 they are associated, it is at present impossible to say; and we are therefore com- 

 pelled to give it provisionally a distinct specific description and name. From 

 the other compound teeth with which it is associated, in the collection, it may 

 be at once distinguished by its more conical principal crown, its large, bony, 

 solid root, to which its relatively small and distant secondary crowns are firmly 

 anchylosed. There is considerable variation in the length of the root, some- 

 times but two, perhaps but one crown being attached to it. 



Figures 1, la, lb, represent the superior and inferior surfaces, and side view 

 in outline of an elongated specimen from St. Fraucisville, Missouri. Figures 



