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, 



U 



f 



Fig. 438. Skull of a Tur 

 tie seen from behind, 1 

 basi-occipital ; 2, exoccipi 

 tal;3, supraoccipital ; 5, basi 

 sphenoid ; 15, prootic (pe 

 trosal) ; 17, quadrate. After 

 Gegenbaur. 



according to Gegenbaur, modified 

 transverse processes. 



The skull of reptiles is much fs 

 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, 

 lias 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- Flf? m ._ Eonea of the foot of a 

 quadrate cartilage, but a small g^fjf f^mur^t t a ib? a % e nbura" 



part Of the true Skull is to be m^m'meiatar^us^^r metatarsi" 



seen. The parts forming the iiao'f tiie 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 

 Zore legs always wanting, in a few forms, as the pythons, 



