SKELETON, 11g 
meeting its fellow in the median line below. The pelvic opening was 
very small. The pelvic bones of the ichthyosaurs were weak, long and 
slender, and apparently were imbedded in the muscles. 
In recent birds (figs. 50, 53) the pelvic bones arefused. The ilium 
is greatly elongate and usually fused with the synsacrum (p. 53); ischium 
Fic. 119. Fic. 120, 
Fic. 119.—Development of pelvis of chick, after Miss Johnson. A, chick of 6 days. 
B, older; C, 20 days; cartilage dotted, bone white. a, acetabulum; 2/, ilium; zs, ischium; 
in, ischiadic nerves; on, obturator nerve; p, pubis; pp, pectineal process. 
Fic. 120.—Pelvis of Galeopithecus, after Leche. ab, acetabular bone; i, ischium; 7, 
ilium; p, pubis; cartilage dotted. 
and pubis directed backward. The pubes, lying in the position of the 
postpubes of the dinosaurs, never meet below except in the ostriches. 
In the embryo (fig. 119) they are at first directed forward and only 
attain the final position later. A pec- 
tineal process arises from the aceta- 
bular region and extends forward, simu- 
lating the dinosaur pubis. 
" Tn the mammals, obturator foramen 
and ischio-pubic fenestra are united, 
the opening being bounded on the 
medial side by processes from ischium yg. r21—Teeft side of pelvis of 
and pubis. All three bones may meet in sora arpa at es on 
the acetabulum, but more often the ex- base Gon ae abitirator foes: 
tension of ilium and ischium excludes ™¢?i?) 0S Pubis; sv, sacral vertebra. 
the pubis from the fossa. A peculiarity is the common occurrence of an 
additional bone in the formation of theacetabulum (acetabular or coty- 
loid bone). This lies between ilium and pubic bone and may fuse with 
any ofthe elements. In marsupials and monotremes the interpubic car- 
8 
