THE INTERNAL SKELETON, 197 
toes only; those of the middle part of our foot answering to the 
greater part of the skeleton of the bird’s so-called “ tarsus.” 
The fenur, or bone of the thigh, is more or less cylindrical 
and expanded at either end. It is short and thick compared 
with the tibia. Its upper end, or head, is rounded and is obliquely 
directed inwards, its long axis being almost at right angles with 
that of the shaft. It bears a deep pit into which a strong liga- 
ment, the ligamentum teres, is inserted and helps to bind it to 
Fig. 158, 
\ 
\\ 

LxeG-Bones OF THE Diver (Colymbus). 
J, Femur; ¢, tibia; p, cnemial process (only found thus developed in the 
Diver and its allies) ; 4, fibula. 
the acetabulum. An upwardly projecting prominence from the 
summit of the shaft is called the trochanter, and it plays against 
the “ antitrochanteric process ” of the pelvis. On the back of 
the femur, below its middle, there may be (as sometimes in 
Swans and Ducks) a prominence into which the femoro-caudal 
muscle is inserted. This may be called the inferior trochanter. 
The distal end of the femur bears two prominences, or con- 
