392 UNGULATA 



is long and slender ; the suprascapular border is rounded, and 

 slowly and imperfectly ossified. The spine is very slightly devel- 

 oped ; rather above the middle its edge is thickened and somewhat 

 turned backwards, but it gradually subsides at the lower extremity 

 without forming any acromial process. The coracoid process is a 

 prominent rounded nodule. The humerus is stout and rather 

 short, and has a double bicipital groove. The ulna is quite rudi- 

 mentary, being only represented by little more than the olecranon. 

 The shaft gradually tapers below, and is firmly ankylosed to the 

 radius. The latter bone is of nearly equal width throughout. The 

 three bones of the first row of the carpus (the scaphoid, lunar, and 

 cuneiform) are subequal in size. The second row consists of a very 

 broad and flat magnum, supporting the great third metacarpal, 

 having to its radial side the trapezoid, and to its ulnar side the unci- 

 form, which are both small, and articulate distally with the rudi- 

 mentary second and fourth metacarpals. The pisiform is large and 

 prominent, flattened, and curved ; articulating partly with the 

 cuneiform and partly with the lower end of the radius. The large 

 metacarpal is called in veterinary anatomy "cannon-bone"; the 

 small lateral metacarpals, which gradually taper towards their 

 lower extremities, and lie in close contact with the large one, are 

 called " splint-bones." The single digit consists of a moderate-sized 

 proximal (os suffmginis, or large pastern), a very short middle (os 

 coronce, or small pastern), and a wide, semi-lunar, ungual -phalanx 

 (os pedis, or coffin-bone). There is a pair of large nodular sesamoids 

 behind the metacarpophalangeal articulation, and a single large 

 transversely extended sesamoid behind the joint between the 

 second and third phalanx, called the " navicular bone." : 



The carpal joint, corresponding to the wrist of man, is commonly 

 called the "knee" of the Horse, the joint betAveen the metacarpal 

 and the first phalanx the " fetlock," that between the first and 

 second phalanges the " pastern," and that between the second and 

 third .phalanges the " coffin-joint." 



In the hind limb the femur is marked, as in other Perisso- 

 dactyles, by the presence of a " third trochanter," a flattened process, 

 curving forwards, arising from the outer side of the bone, about 

 one-third of the distance from the upper end. The fibula is reduced 

 to a mere styliform rudiment of the upper end ; its loAver part being- 

 absent or completely fused with the tibia. The calcaneum has a 

 long and compressed calcaneal process. The astragalus has a large 

 flat articular surface in front for the navicular, and a very small one 

 for the cuboid. The navicular and the external cuneiform bones 

 are very broad and flat. The cuboid is small, and the internal and 

 middle cuneiform bones are small and united together. The meta- 

 podials and phalanges resemble very closely those of the fore limb, 

 1 This must not be confounded with the navicular of the tarsus. 



