386 GEOGRAPHICAL ZOOLOGY. [PART iv. 



region; Echis (2 sp.), inhabiting North Africa to Persia and 

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

 Africa. 



Remarks 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 peculiarity. Yet in their warmer portions they are 

 tolerably rich; for, of the 25 families of snakes, 6 ( are found in the^ 

 Nearctic region, 10 in the Palaearctic, 13 in the Australian, 16 

 in the Neotropical, 17 in the Ethiopian, 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 Ethiopian (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 

 Palaearctic 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 $ ; four of these belong to the Colubridse, 

 one to the Py thonidae, and four to the Crotalidse. The Palsearctic 

 region has only 2 peculiar genera,*; belonging to the Colubridse 

 and Crotalidae. The Ethiopian has 3.C belonging to 11 'families; 

 four to Colubridae, five to Lycpdontidse, and three to Elapidsp. 

 The Oriental has no less than $0, belonging to 15 families ; five 

 are Colubridse, five Uropeltidae, twelve Homalopsidae, six Lyco- 

 dontidse, three Amblycephalidse, eight Elapidse, and v rour Crota- 



