Dr. A. Giinther on the Geographical Distribution of Reptiles, 237 



The above Schema is made to accord with Mr. Sclater's Schema 

 of the geographical distribution of Birds; but in both schemes 

 the calculations made as to the number of square miles to one 

 species cannot be looked upon even as attempts at approxima- 

 tions, in those regions of which a part only has been explored 

 by naturalists. Thus the large space of Central Asia, between 250° 

 and 300" W. long, and between 35° and 50° N. lat., is quite unknown 

 — a space of about 3,000,000 square miles, which cannot be justly 

 taken into account ; and then we should have a ratio of 1 : 275,000. 

 In the ^Ethiopian and Australian region, at least two-thirds of the 

 area mentioned being unknown, we should have on the average a 

 single species to 50,000 square miles for the former, and to 20,000 

 square miles for the latter region. In this way we arnve at least at 

 a more accurate idea of the series in which the regions follow one 

 another as to their respective richness in forms : — 



1. Indian region 1 : 17,000. 



2. Australian region 1 : 20,000 (instead of 1 : 60,000). 



3. South American region 1 : 36,000. 



4. ^Ethiopian region 1 : 50,000 (instead of 1 : 150,000). 



5. North American region 1 : 87,000. 



6. Palaearctic region 1 : 275,000 (instead of 1 : 350,000). 



Thus from the consideration of the geographical distribution of 

 Snakes, we are obliged to acknowledge the views of the primary divi- 

 sions of the earth's surface given by Mr. Sclater as those most 

 natural. I have endeavoured always to state those facts which ap- 

 parently contradict this view, as well as those which favour it ; but, 

 by stating the former, I intend rather to direct the attention of the 

 systematist to such less satisfactory results of his exertions, than to de- 

 stroy the idea of primary ontological divisions. As, however, we do 

 not know one species of Snakes extending fully over two regions, 

 and as we find each region occupied by a majority of peculiar genera, 

 we come to the inevitable conclusion that these different forms of 

 Snakes were created in the different parts of the world where they 

 are now found ; but it would be a too precipitate inference to 

 maintain the same for all other species of the animal kingdom. 

 As I said in the beginning of this paper. Snakes form a most sta- 

 tionary tribe among animals ; but other animals are subjected to 

 internal or external agencies by which they are necessarily spread, 

 in a longer or shorter lapse of time, beyond their primary bound- 

 aries ; and it is a great mistake, in such instances, not to admit the 

 identity of species, even though it be modified into a climatic variety. 

 How the Batrachians are related in this respect, and what are the 

 most natural divisions of the earth's surface as to this order of 

 Reptiles, will be the subject of the Second Part of this paper. 



