50 CARNIVOEA order hi 



compact. The humerus invariably has an entepicondylar foramen, and an 

 undivided distal trochlea, which in higher forms extends as far back as 

 the olecranon fossa. 



The radius, ulna and usually all of the carpal bones remain distinct, but in 

 the Arctocyonidae the scaphoid and centrale are united. Fusion between 

 these bones and the lunar, which is exceedingly common in the true 

 carnivores, occurs exceptionally, and perhaps not at all in some of the later 

 species of Hyaenodon. 



The metacarpals correspond in form, size and arrangement with those 

 of recent carnivores. The distal phalanges may become elongated or 

 even hoof-like (Fachyaena). The ilium is triangular, resembling that of the 

 insectivores and marsupials, and more slender than that of true carnivores ; 

 the femur has a more or less conspicuous third trochanter. The tarsal bones 

 agree essentially in form and arrangement with those of recent members 

 of the order, differing in that the astragalus and calcaneum are more 

 compact and less closely apposed. 



Accoi'ding to Matthew's classification, the Creodontia may be divided into 

 three groups, Acreodi, Fseudocreodi and Eucreodi, the latter being the point 

 of transition to the Carnivm'a vera. 



Tribe 1. ACREODI. 



Molars not of trenchant form, primitive ; superiorly trituhercular, inferiorly with 

 blunted cusps. 



Family 1. Oxyclaenidae Scott. 



Ah specialised carnassial, superior molars tritubercidar, subquadrate or triangular 



in outline ; inferior molars tuberculo-sectorial with 

 angidar cusps, trigonid higher than talonid. 

 P^ simple, P* occasionally simple, P^ with internal 

 : j ; i ; i cusp. 

 PrP? p* rrii nis ms The skeleton is but little known, and 



generic distinction is based entirely on dental 

 characters. From the early Eocene of New 

 Fig. 76. Mexico, Wyoming, and Montana. 



Tricentes subtrigonus Cope. Torrejon beds OxVClaenUS, LoXOlovhxiS, Carchiodon CopS. 



of Lower Eocene ; New Mexico. Upper and ti j ? • n , t^ a ah r .i 



lower dentition. Vi- (After Matthew.) ProtOCliriaCUS bcott. P f. All irom the 



Puerco beds. 

 Chriacus, Tricentes Cope (Fig. 76). Torrejon and Ft. Union beds, associated 

 with Deltatherixmi. P |. 



Family 2. Mesonychidae Cope. 



3-2 



— - — M. Ko carnassials, superior molars and last premolar tritubercular 



with high, blunt-topped cusps. Lower jaw with cusps of teeth arranged serially, the 

 central cusp much the highest, talonid usucdly trenchant or basin-shaped. Manus and 

 pes paraxonic, e.vtremities originally pcniadactyl, later becoming tetradactyl. Humerus 

 with supratrochlear foramen, fibida articulating with calcaneum, claws blunt and 

 hoof-like. Zygapophyses of lumbar vertebrae cylindrical or inrolled. Brain very 

 diminutive. 



