ON THE FLAT-CLAWED CARNIVORA OF THE EOCENE OF 



WYOMING. 



BY EDWARD D. COPK, A. M. 

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



MESONYX. Cope. 



This genus was described by the writer in the Proceedings of the 

 American Philosophical Society for 1872, p. 460, and published in an 

 advance edition of the same paper on July 29th, 1872. It was there re- 

 ferred to the Carnivore, and stated to resemble Hyanodon in some re- 

 spects. I propose on the present occasion to attempt a more exact 

 determination of its structure and relationships. The only species yet 

 certainly referable to it is Mewnyx obtusidens, 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 

 pelvis, 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 Garnivora fissipedia. It becomes interesting 

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

 families now living. 



The cervical vertebrce are damaged. The dorsals are strikingly smaller 

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

 coelian 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 opisthoccelian structure, and are quite depressed in form. 

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

 ing vertebra3 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 

 have interlocking articulations, the posterior with a convex exterior 

 articular face, the anterior with a concave anterior one. The sacrum 

 is not completely preserved, three coossified centra remain. These are 

 more elongate and the diapophyses have less expansion than in Felix. 

 Rywna, Cams or JTrsus. They are much flattened, and the middle one 

 has two slight median longitudinal angles. The caudal vertebrae in- 

 dicate a long tail, with stout base. Its proximal vertebrae are depressed, 

 and with broad anteriorly-directed diapophyses. The more distal verte- 

 brae have sub-cylindric centra ; the terminal ones are very small. 



The glenoid cavity of the scapula is shallow ; the coracoid process is a 

 short hook separated by a strong groove from the edge of the former. 

 The spine is well developed. In the character of the coracoid, this 

 genus resembles Felis more, than Ganis or Ursus. The ulna exhibits 

 little trace of articular face for the radius, less than in Felis or Ganis. 



