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NOTES ON THE GEOGRAPHICAL DISTRIBUTION 
OF ANIMALS. 
By W. F. KIRBY, 
Assistant Naturalist, Museum, Royal Dubllst Society. 
T HE study of the geographical distribution of living and 
extinct organisms has recently become one of the most 
important branches of philosophical natural history, from the 
light which it throws both on the former condition of the earth, 
and on the greatest scientific question of the day, namely, that 
of the origin of species. The geographical distribution of 
animals has lately received much attention, the most important 
contribution to the subject being a large work by Mr. A. R. 
Wallace ; but in the present paper we propose to bring together 
such observations as may prove interesting, either from their 
importance or from their having been less fully discussed else- 
where. 
Most naturalists are now agreed in recognising six main 
regions of geographical distribution, as originally proposed by 
Dr. Sclater, viz. the Palsearctic, Ethiopian (or African), Indian 
(or Oriental), Australian, Neotropical (or tropical American), 
and Nearctic (or North American) regions. The Palsearctic 
region includes Europe, North Africa, the northern half of 
Arabia, and the whole of Western and Northern Asia, as far as 
the Indus and Himalayas, and a line drawn eastwards, running' 
south of Thibet and Mongolia, and somewhat north of Formosa. 
The Indian region includes, besides South Asia, the large 
islands of Borneo, Java, Sumatra, and the Philippines ; but the 
islands further to the east belong to the Australian region. 
The Neotropical region includes the West Indies, Central and 
South America, and the south of Mexico; the remaining 
regions require no further explanation. 
Although these regions are generally recognised as natural, 
we must not consider the divisions between them as hard and 
fast lines, except that between the Indian and Australian 
regions, where the island of Celebes is almost the only de- 
