490 



ZOOLOGY. 



The vertebral column 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, 



Fig. 438. Skull of a Tur- 

 tle seen from behind, 1, 

 basi occipital ; 2, exoccipi- 

 tal; 3, supraoccipital ; 5, basi- 

 sphenoid ; 15, prootic (pe- 

 trosal) ; IT, quadrate. After 

 Gegenbaur. 



according to Gegenbaur, modified 

 transverse processes. 



The skull of reptiles is much ts 

 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- Fig 439 ._ Bones of the foot of a 



miflflratp PirHl'iap linf n <jm-ill Reptile (lizard) A, and an embryo 

 li o e > ' bird, B. A femur ; <, tibia ; p, fibula ; 



part of the true skull is to be to - u PP er ' "- lower P' e r ce8 of the tar - 



. 8us ; TO, metatarsus ; /- V, metatarsa- 



seen. The parts forming the Ha of the toes. 



hyoid suspensorium in fishes (hyomandibular and symplectic 



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



skull. 



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

 2ore legs always wanting, in a few forms, as the pythons, 



