YEETEBRATES. 343 



the majority of specimens, nearly smooth. Root short, thick, oblique, 

 lateral margins slightly converging below, iii breadth much narrower, 

 and in depth less than the hight of the crown. Greatest lateral diame- 

 ter of tooth of medium size .15 inch, or nearly equal to the entire eleva- 

 tion of tooth, hight of concave crown face about .10 inch. 



Of the several individual representatives of this interesting form, 

 those furnished by Dr. Williams, of Boonville, are the most perfect. 

 Xone of the specimens preserve the root entire, and most of them are 

 otherwise mutilated ; but the characters which distinguish them from 

 other forms are sufficiently well displayed in all the examples. In 

 regard to tbe generic relations of these teeth, it seems not improbable 

 that perfect examples might prove them to be distinct from Desmiodus, 

 to which genus they are here provisionally referred, and with which 

 they possess many features in common. The rigid root, vertical crown 

 and rather strong median fold in the convex face, together with the 

 inbeveled coronal belt, present the same general characters which per- 

 tain to the above mentioned genus. They are readily recognized from 

 Z>. minusculus of the same deposits by the stronger and more compressed 

 crown. Thev may, however, hold the same relation to that form as 

 does D. costilliferus to D. tumidus of the St. Louis beds. 



Position and locality : Upper fish-bed horizon of the Keokuk lime- 

 stone, Boonville, Missouri, and Bentonsport, Iowa. 



Desmiodus % flabellum, St. J. and W. 



PI li, Kg. 15. 



Teeth small, moderately strong, flabellate in outline. Crown moder- 

 ately thick, crest broadly arched, lateral margins low and slightly 

 divergent from the ill defined extremities formed by the union of the 

 coronal belt, and irregularly notched by more or less widely spaced, 

 shallow serrations; concave face suboval, lateral diameter and hight 

 nearly equal, gently arched vertically, very slightly arched or nearly 

 plane laterally, with the lateral border slightly raised into a faint mar- 

 ginal rim, basal belt broad, well-defined, rapidly contracted below, and 

 occupying the inbeveled region, upper edge slightly arched upward in 

 the middle and again curved upward in rounding the lateral angles, and 

 marked by a few relatively strong vertical folds in the median region ; 

 convex crown face about one-third less elevated than the opposite face, 

 very gently arched laterally, in which direction it presents a broad, 

 shallow channel in consequence of the slight vertical ridge, coronal fold 

 very similar to that in the opposite face, though slightly narrower, 

 simple, inbeveled, the upper edge approximating the curvature of the 

 crest ; both crown faces marked by short, irregular, diverging, thread- 



