SKELETON. 



Ill 



the ilium is very long and the ischio-pubis is strongly compressed, 

 obturator foramen and ischio-pubic fenestra being absent. 



Omitting the extinct rhynchocephals, whose pelvis resembles that of 

 the stegocephals, the reptiles have the pelvic bones more solid and dis- 

 tinct than do the ichthyopsida; the ilium is strong, with its dorsal end 

 frequently expanded; the ischio-pubic fenestra is large; and ischium 

 and pubis are united to their fellows directly, or by the intervention of 

 the epipubic cartilage, or its modification, the ligamentum medium 

 pelvis. As a rule all three bones meet in the acetabulum and there 

 are large prepubic processes, though these are small in the lizards and 

 are lacking in crocodiles. 



FIG. 116. FIG. 117. 



FIG. 116. Pelvis of snapping turtle (Chelydra) from below, e, epipubis;/, femur; 

 h, hypoischium; I, ligamentum medium pelvis; p, pubis; pp, pectineal process. 



FIG. 117. Pelvis of Iguana tuberculata, after Blanchard. a, acetabulum; e, epipubic 

 cartilage;/, femur; il, ilium; is, ischium; of, obturator foramen; p, pubis; pp, prepubis; 

 s, 1 s 2 , first and second sacral vertebrae. 



Many theriomorphs have the pelvic bones fused much as in mam- 

 mals. In Sphenodon and turtles the epipubic cartilage bounds the 

 fenestra on the median side, and Sphenodon and the plesiosaurs have 

 a separate obturator foramen, but the two are merged in the chelonians. 

 Most lizards have slender pubic bones, perforated by the foramen, and 

 the part of the epipubis between the fenestrae reduced to a ligament, 

 while the posterior part of this, behind the ischium, may ossify as a 

 distinct bone (os cloacae or hypoischium). In the footless lizards the 

 pelvis is reduced, being represented in the amphisbsenans by rudiments 

 of ischium and pubis, while all traces of the pelvis are lost in snakes, 

 except the boas and some opoterodonts. The obturator foramen is 

 very large in the crocodiles, the result of the oblique position of the 



