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MANUAL OF ELEMENTARY ZOOLOGY 



quadrate in the skull, a palate separating nasal passages 

 from the mouth, a sternum and pectoral girdle, one penis, 

 no bladder, and completely separated ventricles. The 

 palate is a structure we have not yet met with. It is 

 supported by flanges of the premaxillae, maxillae, palatines, 

 and pterygoids arching under the primary roof of the 

 mouth and forming a secondary roof. A short partition of 

 this kind, not involving the pterygoids, is found in turtles. 



PP1X 



Fig. 285.— The skull of a turtle.— From Thomson. 



AN., Angular; AR., articular; D., dentary ; FR., frontal; /., jugal ; MX., 

 maxilla; PP., prefrontal; PAR., parietal; PMX., premaxilla ; POF., post- 

 frontal; Q., quadrate; QJ., quadratojugal ; J., surangular ; SO., supraocci- 

 pital ; SQ., squamosal. 



In mammals there is a palate longer than that of the turtles, 

 but not so long as that of crocodiles (p. 437). 



The Tuatara (Sphenodon) is the only living representative 

 of the Rhynchocephalia, the most ancient group of reptiles, 

 lizard-shaped animals without bony armour, with two 

 arcades and a fixed quadrate in the skull, no penis, and 

 an incompletely divided ventricle. The pineal organ of 

 Sphenodon is more highly developed than in any existing 

 vertebrate, and has an appendage which shows a striking 

 resemblance in structure to an eye and lies in a foramen 



