OPHIDIA. 785 



tebrse the hypapophyses are acute keels supporting an angular prominence 

 near the center ; further posterioi-ly there is a slight prominence at the base 

 of the ball. More posteriorly the hypapophysis forms a naiTOw but some- 

 what obtuse ridge, terminating posteriorly in an apical angle at the inferior 

 side of the ball. The neural arches are separated by spaces equal to the 

 lengths of their bases. The rib articulations present the peculiarity of 

 other members of this group, of a single surface, of which the superior half 

 is convex, and the inferior slightly concave. 



Measurements. 



No. 1. — More anterior. 



M. 



Length of centnun 0.0027 



Width of ball OOIG 



Depth of ball 0011 



Width between parapophyses 0020 



Depth of entire vertebra 0034 



No. 2. — More posterior. 



Length of centrum 0.0030 



Width of ball 0017 



Depth of ball 0013 



Width between parapophyses 0023 



Depth of entire vertebra 0040 



From the beds of the White River Epoch in Northeast Colorado. 

 NEURODROMICUS Cope. 



Synopsis of new vertebrata from the Tertiary of Colorado, 1873, p. 15. Annual Report U. S. Geological 



Survey Terrs., 1873 (74), p. 516. 



Centrum small, with a prominent truncate hypapophysis. Neural arch 

 capacious, the zygantrum wider than the articular cup. Neurapophyses 

 bounding the canal laterally below the zygosphene; its border not angulate 

 behind. Parapophysis projecting acutely below centi-um. An elevated 

 neural spine. No process below the prezygapophysis. No prominent ridge 

 connecting the zygapophyses. 



This genus represents a different group of snakes from those included 

 in the three genera above described. The vertebra resembles considerably 

 those from the anterior part of the column of one of the Crotalidce, but 

 differs in the less robust hypapophysis and the absence of the process below 

 the prezygapophysis. 

 50 o 



