786 THE WHITE EIVER FAUNA. 



Neukodromicus dorsalis Cope. 



Locis citatU, 1873, 1874. 

 PlateLVIIIa; figs. 7, 8. 



Articular surfaces of centrum round ; the ball with a slightly upward- 

 looking obliquity. Hypapophysis continued to cup as a prominent carina. 

 Neural spine extending its base forward, so as to stand on the entire length 

 of the neural arch. The rib articular process is of light form, and is sepa- 

 rated by a considerable space from the prezygapophysis. The superior 

 convex portion is quite small, while the inferior portion is narrow and is 

 produced downwards. There is a trace of ridge connecting the zygapoph- 

 yses, and a trace of a groove on each side of the anterior part of the base 

 of the hypapophyses. Both the neural spine and the hypapophysis are 

 thin edged, and all parts of the vertebra are delicate and light, in strong 

 contrast to those of Calamagras and its allies. 



Measurements. 



Length of centrum 0.0045 



„. ^ „ (vertical 0020 



Diameter of cup, < „„„, 



( transverse uu^ii 



Elevation of neural spine above centrum 0055 



Elevation of neural spine above neural arch 0029 



Length of hypapophysis below centrum 0012 



Width of hypapophysis 0011 



The zygantrum is capacious, and the whole neural arch open and 

 light. The species was about the size of the black snake {Bascanium con- 

 strictor). 



The White River Epoch of Northeast Colorado. 



MAMMALIA. 



The White River Epoch was very rich in Mammalia, but not more so 

 than the preceding epochs of the Eocene proper, the Bridger and Wasatch. 

 The composition of the fauna was very diiferent, as a number of important 

 groups of the earlier period wei*e wanting, while several appear for the first 

 time. Of the former kind may be included the Order Amhhjpoda, and the 

 suborders Toeniodonta, Tillodonta, and the family of the Lophiodontidce. The 

 Creodonta and Mesodonta are represented by a very few remnants. The 



