192 LIMBS OF THE SLOTH. 



The iliac bones, 62, repeat the modifications of their 

 honfiotypes the scapula3, and are of unusual breadth as 

 compared with those of other quadrupeds ; they soon be- 

 come anchylosed to the broad sacrum, S, the ischia, 63, 

 and pubes, 64, are long and slender, and circumscribe 

 unusually large "thyroid" and "ischial" foramina, the 

 latter being completed by the coalescence of the tuberosi- 

 ties of the ischia with the transverse processes of the last 

 two sacral vertebrse. The head of the femur, 65, has no 

 impression of a ligamentum teres. The patella, 66', is 

 ossified ; there is a fabella behind the external condyle. 

 The tibia, 66, and fibula, 67, are bent in opposite direc- 

 tions, intercepting a very wide interosseous space. The 

 anchylosis of their two extremities, which, has been found 

 in older specimens, has not taken place here. The inner 

 malleolus projects backwards and supports a grooved 

 process. The outer malleolus projects downwards, and 

 fits like a pivot into a socket in the astragalus, turning 

 the sole of the foot inwards — a position like that of the 

 hand — best adapted for grasping boughs. The calcaneum, 

 68, is remarkably long and compressed. The scaphoid, 

 cuboid, and cuneiform bones have become confluent with 

 each other and the metatarsals, of which the first and fifth 

 exist only in rudiment. The other three have likewise 

 coalesced wuth the proximal phalanges of the toes which 

 they support : these toes answer to the second, third, and 

 fourth, in the human foot. 



The short and small head of the sloth is supported on 

 a long and flexible neck presenting the very unusual cha- 

 racter in the Mammalian class of nine vertebrae, C — the 

 superadded two, however, appearing to have been im- 

 pressed from the dorsal series, D, by their short, pointed, 

 and usually movable ribs. The head and mouth can 



