VEETEBBATES. 297 



above, and its regular parallelism, seem to point to a more intimate 

 relationship with a group of closely allied but genericallydistiuct teeth, 

 which were first made known by Messrs, Newberry and Worthen 

 under the name Lophodus (111. Eep., vol. IV, p. 300), a designation which, 

 unfortunately, is preoccupied, and for which we have substituted Agas- 

 sizodus. But the teeth under consideration lack the very essential char- 

 acters by which the teeth of Agassizodus are distinguished, that is, the 

 strongly buttressed anterior coronal face, in the present teeth both faces 

 presenting the same degree of vertical corrugation. The appearance of 

 the vertical ridges also recall that in Mesodmodus exsculptus ; but they 

 are much more delicate in the present form, while there exists not the 

 faintest trace of the sub-coronal protuberance in the anterior border 

 such as characterizes the above genus. 



Position and locality : Eare in the areno-magnesian beds in the upper 

 part of the Kinderhook formation ; near Eichmond, Washington county, 

 Iowa. 



Orodus Whitei, St. J. and W. 



PI. VI, Fig. 25. 



A unique specimen, discovered by Dr. White, presents a series of 

 eight teeth apparently firmly soldered at their bases into a common 

 basal support, which is remarkable for the slightly spirally inrolled out- 

 line and contour, recalling the shape of the dental plates of some of 

 the CocJiliodonU. Together the teeth occupy a deltoidal figure, of which 

 the diameter in the direction of inrollment nearly corresponds to that 

 of the inner margin, which is broadly rounded and from which the teeth 

 successively and regularly diminish in size, the exterior or oldest tooth 

 of the series being about one-third the greatest diameter of the inner or 

 newest tooth ; the anterior margin is gently arched, while the opposite 

 margin, corresponding to the "'oblique" margin of jDochliodonts, is 

 slightly concave or sigmoidally curved from the subacute postero-inner 

 angle to the outer inrolled extremity ; the median cones of the individ- 

 ual teeth form a prominent coronal ridge, slightly posterior to the 

 median line, which traverses the series from the inner to the exterior 

 extremity. The inferior surface is smooth or faintly striated in the 

 direction of inrollment, transversely marked by obscure sulci, which 

 apparently indicate the former presence of sutures, and though exceed- 

 ingly faintly marked, they correspond in position to the interspaces 

 separating the individual teeth composing the series, and which, as seen 

 from the side, are too apparent to be mistaken. Individually, the teeth 

 comprising the series are quite uniform in appearance, the extreme 

 outer individuals showing unmistakable evidence of attrition from wear 



—39 



