Cope..] -LJo [April 4, 



the amount of verification his results have afforded to my hypotheses. 

 I subjoin his determinations of the mean eccentricities, and the mean 

 perihelia and aphelia which represent those determinations. 



ON THE FLAT-CLAWED CARNIVORA OF THE EOCENE OF 



WYOMING. 



By Edward D. Cope, A. M. 



(Redd before the American Philosophical Society, April 4, 1873.) 



MESONYX. Cope. 



This genus was described by the writer in the Proceeding's of the 

 American Philosophical Society for 1872, p. 460. It was there referred 

 to the Carnivore, and stated to resemble Ilycenodon in some respects. 

 I propose on the present occasion to attempt a more exact determi- 

 nation of its structure and relationships. The only species yet cer- 

 tainly referable to it is Mesonyx obtundent, Cope, 1. c, which is repre- 

 sented by a fragmentary skeleton. There are preserved, portions of the 

 skull with the teeth, chiefly mandibular ; numerous vertebrae from all 

 parts of the column ; parts of scapula, ulna and fore feet ; portions of 

 p dvis, femora, tibiae, tarsals, metatarsals, and phalanges. 



The numerous unguiculate digits, the sectorial character of the molar 

 teeth and the characteristic form of the astragalus demonstrate this 

 genus to belong to the Carnivore;, fissipedia. It becomes interesting 

 then to determine the relations of an Eocene type of the order to the 

 families now living. 



The cervical vertebjrm are damaged. The dorsals are strikingly smaller 

 than the lumbars, being less than half their bulk. They are opistho- 

 ccelian with shallow cups, and the centra are quite concave laterally 

 and inferiorly. The centra of the lumbars are more truncate, with a 

 trace of the opisthocoelian structure, and are quite depressed in form. 

 The median part of the series is more elongate than in the correspond- 

 ing vertebras of the genus Canis. They exhibit an obtuse median longi- 

 tudinal angle, on each side of which, at a little distance, a nutritious 

 artery entered by a foramen. The zygapophyses of the posterior lumbars 



