THE SKELETON. 65 



obturator foramen. The pubis is the ventral portion, pos- 

 sessing two ratni, one projecting laterad to unite with the 

 ilium, cotyloid, and ischium, and the other projecting 

 caudad along the mid-ventral line, joining its fellow and 

 the ischium. In young kittens the junction of these parts 

 is plainly visible, but in adult specimens it is wholly oblit- 

 erated. In old specimens the ischium and pubis become 

 more or less anchylosed with their fellows in the mid- 

 ventral line. The cranial and dorsal border of the ilium is 

 the crest (Fig. 39). The rough crescentic area on the 

 medial aspect is the auricular surface for articulation with 

 the sacrum. The cranial rounded angle of the crest is the 

 anterior superior spine. The anterior inferior spine is the 

 small prominence craniad from the ventral termination of 

 the auricular surface. 



The ischium presents a spine on its dorsal border near 

 the acetabulum. Between this spine and the posterior in- 

 ferior spine of the ilium, is a shallow concavity termed the 

 greater sciatic notch in distinction to the lesser sciatic notch 



<^ 



between the spine of the ischium and the tuberosity. The 

 acetabulum or cotyloid cavity forms the cup for the articu- 

 lation of the femur. The interruption in its ventral border 

 is the cotyloid notch, at whose base there is a depression for 

 the attachment of the ligamentum teres holding the femur 

 in place. The junction of the pubis with its fellow is known 

 as the symphysis. The cranial portion of the bone lying 

 on either side of this is called the body, the caudal part 

 taking the name of ramus. The latter forms part of the 

 boundary of the obturator foramen and meets the ramus of 

 the ischium. This foramen gives passage to the obturator 

 nerve and vessels. 



In the Sirenia, which have no pelvic limbs, the innomi- 

 nate bones are rudimentary. In the Cetacea these bones 

 are also rudimentary, which fact indicates that the ances- 

 tors of these forms possessed functional hind-limbs. 



