84 O. 0. Marsh — Cretaceous Mammalia. 



Cimolomys gracilis, gen. et sp. nov. 



The type specimen of the present genus and species is the 

 upper molar tooth represented on Plate II, figures 1-4. It is 

 apparently from the right side, and is in excellent preservation, 

 the entire crown being complete, and only portions of the 

 fangs wanting. The surface of the crown is divided into three 

 rows of cones. These rows are separated by two deep longi- 

 tudinal grooves. In the outer row, there are seven tubercles ; 

 in the middle row, eight ; and in the inner row, nine. The 

 middle row has the largest elevations, and the inner row, the 

 smallest, those of the outer row being intermediate in size. 



In general structure, the teeth of the present genus are 

 similar to those of Tritylodan, Owen, from the Triassic of 

 South Africa. In the latter genus, however, the upper 

 molar teeth have but three tubercles in each row. This is 

 true, also, of the known teeth of Triglyphus, Fraas, from the 

 Trias of Germany, which is probably identical with Tritylodon. 

 The present genus apparently belongs to the same family, the 

 Tritylodontidce. 



The present specimen is from the Laramie formation of 

 Wyoming. It indicates an animal about as large as a weasel. 



Cimolomys bellus, sp. nov. 



A smaller species of this genus is indicated by an upper 

 molar apparently the last on the right side, which may be con- 

 sidered the type specimen. In this tooth, the inner series of 

 tubercles is not so fully developed as in the corresponding row 

 of the larger species. In the outer row, there are five tuber- 

 cles ; in the middle, six ; and in the inner row, three well- 

 developed cones, and three more of minute size. The crown 

 of this tooth is 5 mm . in length, and 2 mm in width at its widest 

 part. The type specimen is from the Laramie deposits of 

 Wyoming. It indicates an animal of about the size of a 

 mouse. 



Cimolodon nitidus, gen. et sp. nov. 



The teeth of the present genus have the same general 

 structure in the molars as those in the last genus, but there are 

 two rows of tubercles instead of three. The upper molar rep- 

 resented in Plate II, figures 5-8, may be regarded as the t} r pe 

 specimen, and the figures given, three times natural size, will 

 show its characteristic features. In what may be regarded as 

 the outer row, there are eight tubercles, and four only in the 

 inner series. 



This genus represents a new family, which may be called the 

 Cimolodontidce. 



