266 



VERTEBRATE SKELETON 



Apodal lizards have the pelvis reduced (fig. 286, A-C), sometimes to all but 

 complete loss. Some {Bipes. Ophisaurus, Anguis) have the two separate halves 

 of the reduced pelvis attached to the sacrum, all three bones (sometimes fused) 

 being recognizable. 



Most Ophidia have lost all traces of hind limbs and girdles, but a few {Tor- 

 trix, Typhlops, etc.) have isolated bones in the pelvic region (fig. 286, D). These 

 are better developed in some of the larger species {Python, Boa) where all three 

 bones occur, as well as bones of the free limbs. 



The pelvic girdle of Pythonomorphs is lacertihan in type, but reduced in 

 correlation with the loss of supporting function of the hind limbs. 



Chelonia.^ — ^Like the pectoral, the pelvic girdle of turtles is 

 within the bony case, with which it is connected by ligaments or is 



Fig. 287. — Pelvis of Sphargis Hoff- 

 mann, '90). e, epipubis;/o, obturator 

 foramen; il, ilium; is, ischium; p, pu- 

 bis; cartilage stippled. 



Fig. 288. — Pelvis of Chelydra from below. 

 a, acetabulum; e, epipubis; fip, ischiopubic 

 fenestra; il, ilium; is, ischium; p, pubis; pp, 

 prepubis; r, sacral tibs; /, tuber. 



more firmly united. All three bones meet in the acetabulum and 

 the obturator nerve passes through the ischio-pubic fenestra. The 

 long ihum runs ventrally and forwards, its dorsal attachment differ- 

 ing in different groups. In Cryptodires it is attached to the sacral 

 vertebrae and the eighth costal plate; in Trionyx and its alUes to 

 the sacral ribs only, and in all Pleurodires to the carapace and not to 

 the sacral ribs. 



Pubis and ischium are nearly parallel to the plastron, the bones 

 of the two sides meeting in the middle hne. Pubes and ischia are 

 connected by Hgament in Trionychida? and marine turtles (fig. 287); 

 in land and fresh water species by cartilage or bone (fig. 288), these 

 medial structures separating the fenestra.^ of the two sides. Pre- 



