I5o ZOOTOMV. 



100. Each limb of the os innominatum is a separate 

 bone, 'the three meeting in the acetabulum in the tri-radiate 

 suture. 



101. The ilium or dorsal ossification of the innominate 

 bone : it is an irregular rod, flattened from side to side, and 

 passing from its sacral articulation downwards and forwards 

 to the acetabulum, of which it forms the dorsal third. 



102. The pubis or antero-ventral pelvic bone : it is 

 somewhat flattened from above downwards, and forms the 

 antero-ventral third of the acetabulum, whence it takes a 

 direction downwards, forwards, and inwards to meet its 

 fellow in the median symphysis pubis (see dotted 

 outline in Fig. 39). 



103. The prepubis, a small rhomboidal nodule of 

 calcified cartilage, situated in the middle line between the 

 anterior ends of the pubis. 



104. The ischium, or postero-ventral pelvic bone, an 

 irregular flattened bone, forming the postero-ventral third of 

 the acetabulum, and passing downwards and inwards to meet 

 its fellow of the opposite side in the symphysis ischii, a 

 strip of calcified cartilage being interposed between the two 

 bones. 



105. The foramen cordiforme, a heart-shaped space 

 bounded by the pubes in front, and the ischia behind : in the 

 recent state a median ligament divides it into paired 

 obturator foramina. 



106. The os cloacae, a small rod of bone passing horizontally back- 

 wards from the symphysis ischii in the ventral wall of the cloaca ( 176). 



XII. In the hind limb note 



107. Its general composition : it consists of three divisions; 

 a proximal, consisting of a single bone, the femur ; a middle 

 division or crus, consisting of two bones, a larger internal, 

 the tibia, and a smaller, external, the fibula : and a distal 



