THE SUBCLASS PARAPSIDA 269 



Oligocene. Dracaenosaurus Gervais, Protrachysaurus Stefano, 

 France. 



Pliocene. Didosaunis Giinther. 



Tribe Platynota 



Terrestrial or subaquatic lizards from two or three feet to about 

 thirty in length. Epipterygoid and parietal foramen present. Feet 

 pentadactylate, with the primitive phalangeal formula. Sacrals 

 present. 



Family Varanidae. Terrestrial or subaquatic, reaching a length 

 of about thirty feet (Megalania) . Skull more or less elongate, the 

 nostrils rather far back, broadly open. Premaxillae, nasals, and 

 parietals unpaired. Postorbital arch incomplete. Descending plates 

 from the frontals enclose a rhinencephalic chamber. An imperfect 

 joint between angular and splenial. Large palatal openings. Nine 

 cervical, twenty dorsal, vertebrae. Girdles complete. No dermal 

 bones. 



This family, exclusively [Australian], African, and Asiatic, includes 

 but one genus, Varanus, with about thirty living species, none more 

 than seven feet in length.^ Some are subaquatic in habit, seeking the 

 water, in which they swim with freedom by aid of the long flattened 

 tail, to escape their enemies. Their structure is so like that of the 

 following forms of the Dolichosauridae, and especially the Aigialo- 

 sauridae, that it would seem very probable they all had a common 

 origin in early Cretaceous times. Megalania, from the Pliocene of 

 India [and Pleistocene of Australia], is the largest of all known ter- 

 restrial lizards. Unlike most lizards, they have a long protrusible 

 tongue. 



Eocene. Saniva Leidy, North America. Paleovaranus Filhol, 

 Proganosaurus Portis, France. 



Pliocene. Megalania Owen, India. 



Pleistocene. Varanus, India. [Megalania, Australia.] 



Family Dolichosauridae. Slender aquatic lizards, two or three 

 feet in length, with a relatively small skull, long neck of thirteen 



1 [Varanus komodoensis Owens, of the Dutch East Indies, reaches a length of thir- 

 teen feet. — H. C. Raven.] 



