SUBORDER A CREODONTIA 49 



uniform. Auditory bulla rarely ossified. Tail long. Scajjhoid, centrale and 

 lunar usually distinct. Astragalus gently convex superiorly, smooth or only slightly 

 grooved. Terminal phalanges generally broad, obtuse and cloven, flattened inferiorly, 

 more rarely pointed and laterally compressed. Seven lumbar and twelve dorsal 

 vertebrae ; lumbar vertebrae with cylindrical prezygapophyses. 



The group Creodoniia, as first separated by Cope from the Carnivora vera, 

 exhibits genetic relations with the Marsupialia as well as with the Fissipedia, 

 with which they may be united through the family Miacidae, having in 

 common the development of the fourth premolar above and the first molar 

 below as cai-nassial teeth. 



The skull is of the usual carnivore type, large when compared with 

 the trunk and limbs, and having the snout elongated. The cranial cavity 

 is remarkable for its small size, and its narrow elongated form, the auditory 

 bulla being only exceptionally ossified. The brain is diminutive, and with 

 but feAV, faint convolutions. There are no vacuities in the palate as in 

 carnivorous marsupials, although numerous small perforations may exist. 

 Only rarely, as in the Mesonychidae, etc., are the posterior angles of the lower 

 jaw somewhat inflected. 



The dentition exhibits the normal formula „'' /„' , but the incisors, 



0.1.4.0. 



premolars, and molars may become reduced in number although not all 



simultaneously. The dentition difi'ers from that of the carnivorous marsupials 



in having fewer incisors, which increase in size from the first onwards ; and 



from the insectivores in that these teeth are more compactly arranged. The 



canines are strongly developed, conically pointed, and always single-rooted. 



The premolars are distinguished from the molars by their greater simplicity 



and compression, the most posterior frequently simulating morphologically a 



true m,olar, but not developed in the upper jaw as a carnassial tooth like that 



of the Fissipedia. Excepting in the Miacidae, the first lower molar is not 



enlarged more than the others, or otherwise differentiated, and if anything, is 



smaller than the immediately adjoining teeth. The crowns of the superior 



molars are invariably tritubercular, consisting of two outer and one inner 



cusp, the latter generally being united to the former by V-shaped crests. 



They may undergo great changes, the parastyle and metastyle becoming 



very strong. 



The inferior molars are normally tuberculo - sectorial, with pitted 

 talonid ; the metaconid may be very faint or even wanting, while the 

 trigonid becomes shear-like, or sometimes reduced. In contrast to the 

 true carnivores the first lower molar is generally smaller than the succeeding 

 teeth, either the second or third being the largest. The antepenultimate 

 milk molar resembles the last permanent premolar. 



In comparison with the length of the cranium, the extremities are 

 usually shorter than in recent carnivores, and as a rule, stouter and more 



Additional observations on the Creodonta. Bull. Anier. Mas. Nat. Hist., 1901. — The Osteology of 

 Sinopa. Proc. U.S. Nat. IFus., vol. xxx., 1906. — The Carnivora and Insectivora of the Bridger 

 Basin. Mem. Amer. Mns. Nat. Hist. , 1909. — Osborn, II. F., and Wortman, J. L. Bull. Anier. Mus. 

 Nat. Hist., N.Y., 1892 ; 1900. — Schlosser, M., Die Affen, Creodonten, etc., des europaischen Tertiars. 

 Beitrage z. Palaont. Osterr.-Ung., 1887, vi. — Scott, W. B. Journ. Acad. Nat. Sci. Philad., 

 1887-95— Proc. Acad. Nat. Sci." Philad., 1892. — TFori(??i«n, J. L. Bull. Amer. Mus. Nat. Hist., 

 N.Y., 1894, 1899. — Eocene Mammalia in the Marsh Collection. I. Carnivora. Amer. Journ. 

 Sci., 1901, 1902. 



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