PEOFESSOE OWEN ON MACEOPTJS. 433 



In the Kangaroo, as in all Mammals charged with the manipulation of a nursing- 

 pouch, the elbow-joint is fashioned to facilitate the movements of pronation and supi- 

 nation of the fore paw S as well as those of flexion and extension of the forearm. The 

 proximal articular surface of the radius (PI. LXXVIII. fig. 7) is circular, very shallow, 

 at right angles to the shaft or length of the bone. The articular smoothness continued 

 upon the periphery of the head is a little broader (ib. fig. 5, b) where it rotates upon the 

 lesser sigmoid cavity (ib. fig. 8, I) of the ulna, but is narrow where it plays upon the 

 " orbicular ligament." 



The so-called neck (ib. fig. 5, c) is long, and equals the shaft in thickness. The 

 tuberosity (ib. d) rises an inch below the head and is obliquely elongate ; a ridge 

 divides the raised rough surface next the ulna, for the insertion of the biceps tendon, 

 from the smoother tract occupied by the " bursa," intervening between the tendon and 

 the bone. The shaft is slender in proportion to its length ; subtriedral at the proximal 

 third, subquadrate at the distal one (ib. fig. 6). The interosseous line is scarcely developed 

 into a border: it is traceable from behind the tuberosity, along the ulnar side of the 

 shaft, to the distal end, which expands to a little beyond the breadth of the upper 

 part of the shaft at the tuberosity (fig. 5, d). The distal articulation is in a state of 

 epiphysis (fig. 6, e), and forms the broadest part of the bone. 



The ulna (PL LXXVIII. figs. 8 & 9) presents at its proximal end the two continuous 

 articular surfaces known in anthropotomy as the " greater " (a) and " lesser " [h] sigmoid 

 cavities. The " greater " is oblong and concave vertically, transversely convex, save at 

 the " ulnar " part of the lower and broader end ; it is slightly emarginate on each side. 

 The " lesser " cavity is semioval, bent down at right angles with the " greater " from 

 its lower and radial side ; it is moderately concave ; it receives the head of the radius, 

 as the greater cavity does the trochlear part of the distal joint of the humerus. The 

 rather prominent angle between the " radial " [h) and " humeral " (a) articular surfaces 

 represents the " coronoid " process (c). Below this is an oblique ridge and roughness 

 [d') for the insertion of the " brachialis anticus." The olecranon {e) extends about an 

 inch above the joint; it is subcompressed and tuberous terminally. The shaft is more 

 compressed and develops a sharp "interosseous ridge" (PI. LXXVIII. fig. 9,/") from 

 its middle third. 



The length of the ulna is 1 foot 3 lines ; its greatest breadth is 1 inch 2 lines ; its distal 

 end, like that of the radius, was in the epiphysial state (ib. fig. 10, 55) ; it terminates by 

 a " styloid process" which works in a pit of the " os cuneiforme " (ib. c). 



The fore paw is pentadactyle, with divergent and freely movable unguiculate digits. 



The carpus (ib. fig. 10) consists of a scapho-lunar {I s), cuneiform (c), and pisiform 

 {p) in the proximal row, and of the usual four bones in the distal row, of which the 

 unciform [u) is the largest, is interposed between the lunar part of the scaphoid and 



' These movements are least free in CJiceropus, in -which the functional digits of the fore paw are reduced 

 to two (n. & m.). 



VOL. IX. — PART VIII. March, 1876. 3 s 



