518 



THE VERTEBRATE SKELETON. 



tibia and fibula are both large and are commonly ankylosed 

 together at either end. The limb bones are very massive also 

 in the Glyptodonts. 



SIRENIA. In no living Sirenian is there any trace of a 

 hind limb, but in Halitherium a vestigial femur is found, 

 which articulates with the pelvis by a definite acetabulum. 



...4 



FIG. 109. LEFT FEMUR OF AN Ox (Bos taurus) (to the left) ANI> OF 

 A SUMATEAN RHINOCEROS (E. sumatrensis) (to the right), x ^ . 

 (Camb. Mus.) 



1. head. 



2. great trochanter. 



3. lesser trochanter. 



third trochanter. 



shaft. 



condyles. 



In the Mystacoceti among the CETACEA small nodules of 

 bone or cartilage occur connected with the vestigial pelvis, 

 and may represent the femur and tibia. No trace of the 

 skeleton of the hind limb is known in the Odontoceti. 



