SKELETON OF PERISSODACTYLA. 455 



feature, from its great size and forward curvature. Ossification 

 sometimes extends from tlie great trochanter to the third tro- 

 chanter. The rotular surface is distinct from those on the con- 

 dyles. The inner wall of the trochlear surface for the patella is 

 thicker, more prominent, and is prolonged farther up the shaft of 

 the femur than the outer wall is ; the condyles are nearly of the 

 same length. The medullary canal commences at the back part 

 in the upper half of the shaft, and inclines forward and down- 

 ward. The bones of the hind-foot are explained at p. 309, 

 fig. 193. 



In the Tapir, the intercondyloid part of the humerus, fig. 299, 

 53, is perforated, as it is likewise in the Hyrax. I have found 

 the radius, 54, and ulna, 55, partially anchylosed at their distal 

 ends in the Malayan Tapir, and have observed their distal 

 epiphyses to coalesce with each other before uniting with their 

 respective shafts. The carpus resembles that in Rhinoceros ; but 

 the unciforme is rather larger, and supports the metacarpal of a 

 fifth, as well as of a fourth digit. The first or trapezial digit is 

 absent, and the one articulated to the magnum, answering to the 

 third, is the largest and of symmetrical shape, the whole fore-foot 

 plainly showing the perissodactyle type, though mth four toes. 

 The little Hyrax and an extinct hornless Rhinoceros {Acero- 

 tlieriuiTi) have a similar unsymmetrically tetradactyle fore-foot. 

 That of the Macrauchenia was tridactyle. The expanded part 

 of the ilium of the Tapir, ib. 62, is an oblong quadrate plate with 

 the upper and hinder angle articulating with the sacrum. The 

 canal for the medullary artery of the femur, which begins near 

 the small trochanter, extends downward to a small medullary 

 cavity at the middle of the shaft, 65 ; which is longer than that of 

 the tibia, 66. The bones of the hind-foot closely resemble those 

 of the Khinoceros, forming the same number of toes : the heel- 

 bone, d, is more prominent. 



In fig. 190, 'bones of the fore-limb of the Horse,' the supra- 

 scapular cartilage is ossified and confluent with the base of the 

 scapula, ^ : o is the infraspinal fossa, p the supraspinal fossa, i the 

 prominent and thickened part of the spine, h the neck, m the an- 

 terior border or ' costa,' I the posterior ' costa ; ' the line from n to 

 n marks the base of the scapula supporting the suprascapula ; k is 

 the coracoid protuberance. In the humerus, a is the shaft of the 

 bone, h the lower part of the deltoid ridge where the ' teres 

 major ' is inserted, e is the great tuberosity which is grooved by 

 the tendon of the biceps,/* is the ' neck.' The proximal epiphysis 

 of the young bone forms both the head and the tuberosity. At 



