550 GEOLOGICAL SURVEY OF THE TERRITORIES. 



Meamirements. 



M. 



Length dental line 0.0148 



Length of lant molar 0030 



Length of antc-pcunlfr 0025 



Width uf ante-peniilt OD-^O 



Length of throe molars preserved 0070 



From the Bridger Beds of the upper valley of Green River. 



CAENIVOEA. 

 MESONYX, Cope. 



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

 American *]*hilosopliical Society for 1872, p. 400, and published in an 

 advance edition of the same paper on July 20, 1872. It was there 

 referred to the Carnivora, and stated to resemble Hucciiodon in some 

 respects. 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 j\[csonyx ohtusidens, Cope, 1. c, which is repre- 

 sented by a fragmentary skeleton. There are preserved portions of 

 the skull with the teeth, chiefly mandibular ; numerous vertebra3 from 

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

 of i)elvis, femora, tibiic, tarsals, metatarsals, and phalanges. 



The numerous uiiguiculate digits, the sectorial character of the molar 

 teeth, and the characteristic form of the astragalus demonstrate this 

 genus to belong to the Carnivorafissipcdia. It becomes interesting, then, 

 to determine the relations of an Eocene type of the ordei" to the families 

 now liviug. 



The ceryical vcrtchrw are damaged. The dorsals are strikingly smaller 

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

 CKjelian 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 opistha^lian structure, and are quite depressed in form. 

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

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

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

 tery entered by a foi-amen. The zygapophyses of the posterior lumbars 

 have interlocking articulations, the posterior with a convex exterior ar- 

 ticular face, the anterior with a concave anterior one. The sacrum is 

 not completely i^reserved ; three co-ossified centra remain. These are 

 more elongate and the diapophyses have less expansion than in Fclis, 

 El/ana, Canis, ovUrsus. They are much flattened, and the middle one 

 has two sliglit median longitudinal angles. The caudal vertebriTe indicate 

 a long tail, with stout base. Its proximal vertebrtB are depressed, and 

 with broad anteriorly-directed diai)ophyses. The more distal vertebrai 

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



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

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

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

 genus resembles Fclis more than Canis or Ursus. The ulna exhibits 

 little trace of articular face for the radius, less than in Fclis or Canis. 

 Its humeral glenoid face is more convex transrersely in its anterior or 

 vertical portion than in those genera, and a little more than in Ursus. 

 In the hind limb the femur resembles that of other Carnicora in all 



