xm 



PHYLUM CHORDATA 



365 



as in the skull of a Bird. The quadrate is immovably fixed to the skull. 

 In the pectoral arch the scapula and coracoid are long and slender, like 

 those of Birds : pro-coracoids and clavicles are absent. The pelvis and hind- 



tmx 





FIG. 1030. Skull of Scaphognathus. D. pre-orbital aperture ; Fr. frontal ; Ju. jugal, 

 MX. maxilla ; N. nasal opening ; Pmx. premaxilla ; Qu. quadrate. (After Zittel.) 



limbs are weak as compared with the fore-limbs, and the pelvis does not 

 exhibit any resemblance to that of Birds, but appears to come nearer to that 

 of the Crocodiles. The astragalus sometimes unites with the tibia. There 

 is no trace of any exoskeleton. The brain, as shown by casts of the interior 





BP 



of the skull, bore interesting resemblances to 

 that of Birds in the relations of the cerebellum 

 and optic lobes, the latter being separated from 

 one another by the approximation of the cere- 

 bellum to the fore -brain, instead of being in 

 close apposition with one another as in existing 

 Reptiles. 



The Pterosauria are confined to formations 

 of the Jurassic and Cretaceous periods. 



PYTHONOMORPHA. 



The Pythonomorpha were large marine Rep- 

 tiles with extremely elongated snake-like bodies, 

 but with well-developed limbs, which were 

 modified as swimming-paddles. The vertebrae, 

 which are very numerous, are proccelous, some- 

 times with, sometimes without, zygosphenes and 

 zygantra. The sacrum is absent as a rule. A 

 sternum has been found in one genus. The 

 skull resembles that of a Lizard, both in form 

 and structure ; the quadrate is mobile ; there is 

 a parietal foramen ; the premaxillse are united. 

 There is no inferior temporal arch, the quadrato-jugal being absent. The 

 quadrate is movable, articulating with the squamosal and epiotic. The rami 

 of the mandible are united by ligament at the symphysis. The pectoral arch 

 (Fig. 1032) comprises discoidal coracoids (c) which meet ventrally, and a 



FIG. 10:51. Rampho- 

 rhynchus, restored. 

 (After Zittel.) 



