386 GEOGRAPHICAL ZOOLOGY. [part iv. 



region; EcJiis (2 sp.), inliabiting North Africa to Persia and 

 to Continental India ; and Athcris (3 sp.), confined to West 

 Africa. 



Reiiiarhs on the General Distribution of Ophidia. 



The Ophidia, being preeminently a Tropical order — rapidly 

 diminishing in numbers as we go north in the Temperate Zone, 

 and wholly ceasing long before we reach the Arctic Circle — we 

 cannot expect the two Northern regions to exhibit any great 

 variety or peculiniity. Yet in their warmer portions they are 

 tolerably rich; for, of the 25 families of snakes, G are found in the 

 Nearctic region, 10 in the Pal?earctic, 13 in the Australian, 16 

 in the Neotropical, 17 in the Etliiopian, and no less than 22 in 

 the Oriental, which last is thus seen to be by far the richest of 

 the great regions in the variety of its forms of Ophidian life. 

 The only regions that possess altogether peculiar families of this 

 order, are the Etliiopian (3), and the Oriental (2) ; the usually 

 rich and peculiar Neotropical region not possessing exclusively, 

 any family of snakes ; and what is still more remarkable, the 

 Neotropical and Australian regions together, do not possess a 

 family peculiar to them. Every family inhabiting these two 

 regions is found also in the Oriental; and this fact, taken in con- 

 nection with the superior richness of the latter region both in 

 families and genera, would indicate that the Ophidia had their 

 origin in the northern hemisphere of the Old World (the ancient 

 Palrearctic region) whence they spread on all sides, in successive 

 waves of migration, to the other regions. The distribution of the 

 genera peculiar to, or highly characteristic of, the several regions 

 is as follows : — 



The Nearctic possesses 9 ; four of these belong to the Colubrida?, 

 one to the Py thonidae, and four to the Crotalidte. The Palwarctic 

 region has only 2 peculiar genera, belonging to the Colubridie 

 and Crotalidse. The Ethiopian has 25, belonging to 11 families ; 

 four to Colubridte, five to Lycodontidre, and three to Elapidse. 

 The Oriental has no less than 50, belonging to 15 families ; five 

 are Colubridte, five Uropeltidre, twelve Homalopsidse, six Lyco- 

 dontida^, three Amblycephalidse, eight Elapida^, and four Crota- 



