xirr 



PHYLUM CHORD AT A 



are weak as coiupaieil willi tlii' forc-liinlis, and tin; pelvis docs nol exiiiliil 

 any i-esemblance to that of Birds, but apjjcars to eome nearer to that of the 

 Crocodiles. The astragalus sometimes unites with the tibia. There is no li-ace 



of any exoskeleton. Tiic biaiii, as sliowu Ijy 

 casts of the interior of the skull, bore interesting 

 resemblances to that of Birds in the relations of 

 the cercliullum and optic lobes, tlie latter being 

 separated from one; another by the appioximation 

 of the cereljellum to the fore-brain, instead of 

 being in close apposition with one another as in 

 existing Reptiles. 



The Pterosanria are confined to formations of 

 the Jurassic and Cretaceous periods. 



Pythonomorpha. 



The Pythonomorpha (Fig. 1021) were' large 

 marine Reptiles with extremely elongated snake- 

 like bodies, but with well-developed limbs, 

 which were modified as swimming-jiaddles. The 

 vertel)ra% which are veiy numerous, are proccelous, 

 sometimes with, sometimes without, zygosphenes 

 and zygantra. The sacrum is absent as a rule. 

 A sternum has been found in one genus. The 

 skull resembles in form that of a Lizard, Ijoth 

 tlie quadrate is mobile, there is a parietal foramen ; 

 the premaxillfc are united. Tlicre is no inferior temporal arch, the quadrato- 



Fic lOJo. — Rampho- 

 rbynchus, rcstnred. 

 (AfturZittel.) 



in foi'm and structure 



Fig. 1021. — Edestosaurus (Pythonomorpha). 

 pro-coi-acoid ; />. humerus ; mr. metacariins 

 V, fifth digit. (From Zittel, after Marsh.) 



Pectoral arch and fore-liiiihs. c. coracoid with 

 )•. radius ; sc. scapula ; m. ulna ; /, flr.st digit ; 



jugal being absent. The quadrate is movable, articulating with the squamosal 

 and epiotic. The rami of the mandible aie imited by ligament at the sym^jhysis. 

 The pectoral arch (Fig. 1021) comprises discoidal coracoids (c) which meet 



