NO. 1449. THE OSTEOLOG Y OF SINOPA—MA TTHE W. 225 



large, both broad and deep, lies mainly proximal to the unciform, 

 nearly touches the lunar internally, and its ulnar facet faces chiefly 

 proximal. The magnum, with very small dorsal surface, is nuich com- 

 pressed laterally and strongly keeled on the proximal side toward the 

 ventral surface. It carries no hook. The trapezoid is not preserved, 

 but from the arrangement of the adjoining bones it appears to have 

 been quite small, its height much less than in Hycenodotu with very 

 slight contact with the magnum, a small dorsal-external contact with 

 the scaphoid, and principally supporting the centrale. Its contact with 

 the trapezium appears to have been lateral-superior. The trapezium 

 is not preserved, but from other specimens it is known to have been 

 rather large, not as high as in Jlyivnodou^ and permitting a greater 

 divergence and more freedom of motion of the poUex, which can 

 hardly, however, be said to be even semi-opposable. 



The metacarpals are five in number, all being of approximately 

 equal robustness, but the laterals reduced in length, although much 

 longer than in Ilysenodon. The exact proportions can not be deter- 

 mined from this specimen, l)ut apparently they were the same as in 

 the manus of Tritemnodon. The tifth digit is restored somewhat too 

 long in the drawing. In Swojyrr and Trittiiniodon^ as in Tlyxnodon^ 

 the symmetry of the manus is pentadactyl with a tendency to tridac- 

 t\dism more marked in the oligocene genus. In the true Carnivora, 

 and in the MesonychidtB among C^reodonts, the manus is constructed 

 upon a tetradactx'l symmetry. 



The phalanges are not remarkable. The unguals are small, more 

 compressed than in Hymnodon^ and fissured at the tips. 



The manus of Trlteianodon agrees in all its pi-incipal features with 

 that of Sinopa, but dift'ers in numerous small details of structure, the 

 greater part of which are slight approximations toward the Hyxnodon 

 manus. 



Hind Ihah. — The pelvis has the same proportions between pre- and 

 post- acetabular regions as in Ilyi^nodon., about the same as in the cat. 

 The superior border of the ilium is considerably expanded, a remark- 

 able character which finds its nearest analogue in the Phenacodontida?, 

 although seen to a less extent in Hyaenodon and IIoplo2>ho7ieus. In the 

 modern Carnivora it is the inferior border of the ilium (below the 

 primitive rod, and below the sacral articulation) which is expanded to 

 a greater or less degree. The ischium is rather thin and slender and 

 the pubis stout, as compared with modern Carnivora. 



The femur is of moderate length, having about the same proportions 

 is in Ilymnodon. The upper part of the shaft has a considerable 

 lateral curvature. The third trochanter is much better developed than 

 in Ilymtiodon^ and placed considerably lower down on the shaft than 

 n Daphmnus or Iloplophmeiis. In modern Carnivora the third tro- 

 Proc. N. M. vol. XXX— 06 15 



