112 



COMPARATIVE MORPHOLOGY OF VERTEBRATES. 



pubes, which do not unite with each other; each is tipped with car- 

 tilage (? separate epipubes). All three bones meet at the acetabulm 

 which is perforate in recent species. The lower end of the ilium sepa- 

 rates as a distinct bone (pars acetabularis). 



The pelvis of the dinosaurs has the same great extension of the ilium 

 forward and back as is seen in the birds and a corresponding in- 

 crease of the sacrum (p. 53), the result of the partially upright position. 



FIG. 118. Pelvis and hind limb of Camptosaurus, after Marsh. /, femur; fb, fibula; il, 

 ilium; is, ischium; p, pubes; pp, postpubis; t, tibia; I-IV, digits. 



The ischia are greatly elongate and are directed backward, being fre- 

 quently united below. The pubic bones are remarkable in being 

 directed forward and downward and in , having strong postpubic 

 processes which are parallel to the ischium. Frequently the ilium 

 gives off an iliac spine near the acetabulum. 



The pterodactyls had the same elongate ilium as the dinosaurs, the 

 ischium being fused to it so as to exclude the pubis from the acetab- 

 ulum, the latter 1 being usually loosely articulated to the ischium and 



1 This pubis is sometimes regarded as a prepubis, the ischium being called an ischio- 

 pubis. 



