490 



ZOOLOGY. 



The vertebral columii is now more distinctly marked off 

 than in the Batrachians : a cervical and lumbar region being 

 indicated in most reptiles except the snakes and turtles. Well- 

 marked ribs exist in nearly all the vertebrae of the trunk, 

 except in the turtles, where the so-called ribs are possibly, 



r\ I r\ 



rig. 438.— Sknll of a Tur- 

 tle seen from behind, 1, 

 hasi-occipital ; 2. esoccipi- 

 tal;.3, stipraoccipital;.5, basi- 

 sphenoid ; 15. prootic (pe- 

 trosal) ; 17. qnadxate. — After 

 Gegenbaur. 



according to Gegenbaur, modified 

 transverse processes. 



The skull of reptiles is much 

 more like that of birds than of 

 Amphibians. There is a single 

 occipital condyle, and the lower 

 jaw is articulated by the quad- 

 rate-bone to the base of the skull. 

 The primitive skull, or that part 

 immediately enclosing the brain, 

 has an incomplete roof, but still 

 is more bony than in Batrachi- 

 ans ; while owing to the great 

 size of the bones developed orig- 

 inally in and from the palato- 

 quadrate cartilage, but a small l^\t^^A\'^^<.Tvl^^\ 



part of the true skull is to be &. upper, a. lower pieces of the tar^ 

 ^ . • 1 ™* ! '" ■ meiatarsns ; /- T, metatarsa- 



seen. The parts forming the Ua of the loes. 



hyoid susiiensorium in fishes (hyomandibular and symplectic 



bones) are, us in the Batrachians, entirely separate from the 



skull. 



While the limbs are, as a rule, absent in the snakes, the 

 £ore legs always wanting, in a few forms, as the pythons. 



Fig. 439.— Bones of the foot of a 



