4 



and the claws flat, -and altogether without prehensile use, but rather 

 adapted for aquatic life. The number of molars exceeds that in any re- 

 cent family of Carnivora except the Protelidat-, and their sectorial form al- 

 lies it at once to the extinct Hycenodontida. To this family the genus 

 Mesonyx may indeed be for the present referred. Among recent families 

 it approaches nearest the Canidw, but has structures borrowed from 

 others, while its numerous molars constitute a point of greater general- 

 ization than any. Although sectorials, this character is not nearly so 

 marked as in the existing Carnivora, the cutting edge being obtuse and 

 occupying half the crown only, while the elevated cone occupying the 

 remainder distinguishes the genus from these and from Hycenodon also. 

 The lobe corresponding to this cone is preceded in Hycsnodon by a 

 cutting edge, in Mesonyx by a tubercle. 



MESONYX OBTUSIDENS. Cope. 



Proceedings American Philosophical Soc. 1872, 460 (July 29th). 



This species was as large as our largest wolves. While the proportions 

 of the limbs were not very different, the form was rather more slender 

 behind. The orbit was smaller, and the cheek bone more prominent 

 than in those animals. The long tail added to the general resemblance 

 to the dogs. The measurements are as follows : 



M. ' 



Length malar bone 0.073 



Depth " in front 016 



"' " at postorbital angle 023 



44 ' middle of orbit 015 



Thickness " " " 013 



Transverse diameter glenoid cavity of scapula. .-. 025 



" ulnar do. for humerus 014 



Length centrum dorsal vertebra 019 



Diameter " transverse 018 



vertical : .014 



Length centrum of a median lumbar 030 



Diameter ' ' transverse 025 



vertical 016 



" first sacral 014 



** " transverse " 026 



Expanse of do 046 



Length of two sacral vertebrae 049 



" proximal caudal 022 



Expanse diapophyses " 036 



Diameter centrum do., vertical 009 



" " transverse 015 



" " distal caudal, vertical 007 



" do., transverse 007 



