THE LIZARD. 151 



division or pes, consisting of a tarsus or ankle, and of five 



digits. 



108. The position of the bones: the femur is directed 

 from its proximal end forwards, upwards, and outwards ; the 

 tibia and fibula pass from their articulation with the femur 

 almost directly downwards; and the digits are directed 

 forwards and outwards. 



109. If the limb is extended at right angles to the long 

 axis of the trunk, it presents, like the fore-limb ( 91), 

 dorsal and ventral surfaces, and pre- and post-axial borders : 

 it is then found that the tibia is pre-axial, and the fibula 

 post-axial, and that, in the ordinary position of the parts, the 

 pre-axial border, in all three divisions of the limb, is internal. 



no. The femur, a stout, slightly-curved bone, consisting 

 of shaft and epiphyses, the proximal epiphysis being, how- 

 ever, hardly distinguishable in the adult. The proximal end 

 of the bone is produced into a prominent ovoidal head for 

 articulation with the acetabulum ; below and internal (pre- 

 axial) to the head is a large process representing the lesser 

 trochanter; the post-axial greater trochanter is almost 

 obsolete. The distal end of the bone is pulley-shaped, and 

 forms internal (pre-axial) and external (post-axial) 

 condyles for articulation with the tibia. Immediately above 

 (proximal to) the external condyle is a process serving for the 

 articulation of the fibula, and answering to the external 

 tuberosity. 



in. The tibia, a stout, greatly-curved bone, consisting 

 of shaft and epiphyses : along its anterior (dorsal) face runs 

 the longitudinal cnemial ridge, which is especially 

 pronounced at the proximal end, giving the bone a triangular 

 transverse section : the proximal end presents two surfaces, 

 the internal and external tuberosities, for articulation 

 with the condyles of the femur. 



