606 MAMMALIAN ANATOMY 



The dorsal surface forms almost a right angle with the proximal 

 surface. It is directed to the radial as well as to the dorsal side, and 

 resembles the surface just described, but can be distinguished from it 

 by its roughness and by the absence of the transverse groove. The 

 radial border is straight. The ulnar border is sinuate, and the distal 

 end is produced in a decided angle. The dorsal surface gives attach- 

 ment to ligaments. 



The palmar surface is very small and triangular, with the base of 

 the triangle facing the scapho-lunar, and the apex, which is directed 



FIG. 467. 



Palmar Side. 



/>^ With Scapho-lunar. 

 With First Melacarpal- ' ^ ' 



Radial Side. ^^^i &^j Ulnar Side. 



-With Trapezoid. 



Dorsal Side. 



LEFT TRAPEZIUM, PROXIMAL SURFACE. 



distally, formed by the palmar termination of the sharp ridge which 

 divides the radial from the ulnar surface. The surface faces inward 

 and backward ; it gives attachment to ligaments and to the flexor 

 brevis pollicis muscle. 



The radial surface (Fig. 468) is regularly crescentic in outline. 

 Well -denned margins separate it from the dorsal surface in front, the 



FIG. 468. 

 Proximal Side. 



Palmar Side. jf^l Dorsal Side. 



With First Metacarpal.' ^^ 



Distal Side. 



LEFT TRAPEZIUM, RADIAL SURFACE. 



proximal surface above, and the palmar surface behind, and the sharp 

 emarginate border below divides it from the ulnar surface. It is 

 saddle-shaped, concave from above downward, and convex from before 

 backward, and faces radially, distally, and to the palmar side. It 

 articulates with the base of the first metacarpal. 



The ulnar surface (Fig. 469) is also crescentic in outline, and is 



