58 THE SKELETON OF THE FROG. 
Each half presents on its outer aspect a cup-shaped cavity— 
the acetabulum—forming with the thigh bone, the hip-joint: we 
accordingly distinguish an iliac portion above the acetabulum, 
and an ischio-pubic portion below it, corresponding respectively 
to the scapular and coracoid divisions of the pectoral girdle. 
i. The ilium: forms the anterior and upper half of 
the acetabulum, and extends forwards as an 
elongated laterally-compressed bar, which is 
attached in front to the transverse process of the 
sacrum and bears along its dorsal surface a 
prominent vertical ridge of bone, the iliac crest, 
ending behind in an abrupt vertical border. 
Posteriorly the two ilia meet one another and 
are united together in the median plane to form 
the iliac symphysis. 
ii. The pubes: consists entirely of cartilage: forms 
the anterior portion of the ventral division of the 
girdle, and therefore corresponds to the pre- 
coracoid in the pectoral girdle. The two pubes 
are completely fused together in the median 
plane, and form only a very small portion, about 
one-sixth, of the acetabular cavities. 
iii, The ischium: the posterior portion of the ventral 
division; corresponding therefore to the coracoid 
in the shoulder girdle. Forms the posterior 
third of the acetabulum. The two ischia are 
completely fused together in the median plane. 
4, The hind-limb. © 
The bones have the same general characters as those of the’ 
fore-limb, to which they correspond very closely. 
a. The thigh. 
i. The femur: a long slender bone expanded at both 
ends, and curved slightly in a sigmoid manner. 
The proximal end or head is spheroidal, and fits 
into the acetabulum to form the hip joint: the 
distal end is somewhat expanded laterally. 
