DISTRIBUTION 121 



like Tropidonotus, Zamenis, and Coluber, extend over 

 the Europo-Asiatic and North American regions, but 

 they are equally well represented in the Oriental. 

 The great difference between Madagascar and Africa 

 is, as we have said, very striking. Madagascar pos- 

 sesses Boidae generically identical with those of South 

 America, but otherwise only Typhlopidae, Colubrinae, 

 and Dipsadomorphinae ; whilst in the greater part of 

 Africa the Boinae are replaced by the Pythoninae, and 

 the Glauconiidas, Elapinae, and Viperinae are gener- 

 ally distributed. North America agrees with Asia 

 and South America in its Crotalinae, otherwise its 

 Ophidian fauna is not very different from that of 

 Europe, although much richer, and South America 

 shares the Glauconiidae with Africa and the Ilysiidae 

 with Southern Asia. South America is rich in 

 Colubrinae and Dipsadomorphinae, nearly all generi- 

 cally different from those of other parts of the world, 

 and the Elapinae are represented by the single genus 

 Elaps, with many species, two of which extend to 

 the southern parts of North America. 



This rapid sketch of the principal facts of Ophidian 

 distribution suffices to show how difficult it would be 

 to frame geographical regions that would give expres- 

 sion to these facts. Such regions would necessarily 

 be very different from those adopted in dealing with 

 the distribution of the other divisions of the class 

 Reptilia. This is a task which need not be attempted 

 on the present occasion. 



