MATTHEW, CLIMATE AND EVOLUTION 



285 



partly to the extinct genus Diplocynodon, in which the proportions of the 

 skull are like Alligator, but with a notch for the lower canine, like Croco- 

 dilus, while the armor, especially the belly armor, is like that of Caiman. 

 North American Tertiary Crocodilia are all with one exception referred 

 to Crocodilus, but the armor is incompletely known, and they may prove 

 also to include Diplocynodon. Gavialis is recorded from the late Tertiary 

 of India; Tomistoma and Crocodilus occur in the Oligocene of Egypt 

 and Tomistoma in the Miocene of southern Europe. The common Egyp- 



FiG. 32. — Distribution of the Crocodilidw 



Originating probably in Cretaceous Holarctica, they have been restricted to the pe- 

 ripheral continents by inability to become adapted to cold climates. Note discontinuous 

 occurrence of crocodiles and of alligators, the last the most specialized, as Caiman and 

 Osteolwmus are the most primitive of the living genera. 



tian Oligocene species of Tomistoma is intermediate between this genus 

 and Gavialis. 



The Upper Cretaceous crocodiles are nearly allied to those of the early 

 Tertiary. 



The Jurassic and Comanchic crocodiles include also long-snouted 

 gavial-like forms, more or less marine in habitat, and broader-snouted 

 crocodile or alligator-like forms of more strictly fresh-water habitat. All 



