EXTINCT MAMMALIA OF NORTH AMERICA. 441 



jaw appears to indicate a genus different from any of tliose now living. The jaw 

 fragment is about nine inches long, straight and ovate in cross section. The basal 

 portion is demi-cylindroid ; the upper portion presents a sub-acute gingival border, 

 with an internal row of large and nearly equidistant neuro-vascular canals, directed 

 upward and moderately forward. The outer side is strongly convex, and near its 

 upper border presents two neuro-vascular canals, larger than those nearer the edge 

 internally and directed more obliquely, forward. All the neuro-vascular canals com- 

 municate with a longitudinal canal, of the form of the jaw fragment, and fourteen 

 lines in its longer and eleven lines in its shorter diameter. The inner surface of the 

 fossil, less convex than the outer, at its lower part presents a deep and proportion- 

 ately wide fissure, extending the length of the specimen, for the accommodation of the 

 Meckelian cartilage. The depth of the fragment anteriorly is forty-three lines; pos- 

 teriorly fifty-one lines. The transverse diameter anteriorly is thirty-four lines ; pos- 

 teriorly thirty-three lines. 



Of two vertebrse accompanying the jaw fragment, judging from the general appear- 

 ance, either, if alone, would have been viewed as belonging to the same individual, but 

 one is mature while the other is devoid of epiphyses. Both are from the lumbar 

 region, and are proportionately longer than the corresponding bones of Balcena or 

 Pi-oiohaI<x?Ki. The sides of the body, below the transverse processes, are deeply de- 

 pressed or concave, so as to produce a prominent median carina inferiorly. The 

 measurements of the specimens are as follow : 



Length of body inferiorly, ...... 



Depth of bod)' anteriorly, . . " . 



Breadth of body anteriorly. 



Width of spinal canal at middle, . . . 



ESCHRICHTIUS. 

 £sclirichtius priscus. 



Balsena j^risca, Leidy : Proc. Acad. Nat. Sc. 1851, 308 ; Anc. Fauna Nebr. 1853, 8. Cope : Proc. 



Ac. Nat. Sc. 1867, 132. 

 Bahcnoptera prisca, Cope : Proc. Acad. Nat. Sc. 1867, 144, 147 ; 1868, 192. 

 UschricJitius iiriscus, Cope: Proc. Ac. Nat. Sc. 1869, 11. 



Founded on a jaw fragment, accompanied by a mature caudal vertebra, from tiie 

 miocene formation of Westmoreland County, Virginia. 



The jaw fragment is about fourteen inches in length and is of slender proportions. 

 It is demi-cylindroid, feebly convex internally and slightly curved downward as well 

 as inward. It is of nearly uniform depth and thickness. The base forms an obtuse 

 or rounded ridge at the boundary of the inner and outer surfaces. The upper margin 



Adult. 



Younc 



Inches. 



Inches, 



7 



6 



5} 



5i 



6 



6J 



2i 



U 



