OF CONCHOLOGY. 17 1 



These three points prove that this zone of creation may be 

 divided into three well distinguished parts, each forming a 

 particular creative centre. 



The first centre includes Spain, extending from the Pyren- 

 nees to the south of Morocco, Algiers, and Tunis. The second 

 extends from the French Alps, following the mountain chains 

 to the east towards the Bosphorous and Black Sea, and to the 

 south to the extremities of the Italian and Hellenic peninsulas; 

 and the third is found from the eastern borders of Anatolia 

 along the Taurian chain towards the Persian and Caspian 

 Seas; it includes Caucasia, Crimea, the Isle of Crete, Cyprus, 

 etc. 



It is a singular fact, says our author, that to the south of 

 these three grand centres, there does not exist any other spe- 

 cial fauna, and that the vast regions of the Sahara, Tripoli, 

 Egypt, Arabia Petrea, Mesopotamia, and Persia are void of 

 special species, making an immense line of demarcation between 

 the great European and the African and Asiatic centres. 



In the Sahara and Tripoli all the species of terrestrial or 

 fluviatile shells belong to the Spanish fauna, except Melania 

 tuberculata from the African. In Egypt nearly all the terres- 

 trial species are Syrian, while the fluviatiles are descended from 

 the African centre, introduced by the Nile. In Mesopotamia 

 the shells are Syrian ; and all the species of Persia are Arme- 

 nian in origin. 



To the north of these creative centres M. Bourguignat finds 

 the same facts governing the distribution of the species as to 

 the south of them ; the vast countries extending from the Alps 

 to the Arctic Ocean containing almost entirely species having 

 their origin in the Alpine system. 



As the result of his studies of the principles of geographical 

 distribution, M. Bourguignat presents the following sum- 

 mary : — 



" 1. The centre of creation of each species is simple, and not 

 multiple. 



" 2. The species of the European system have their creative 

 centre in the mountainous countries, and not in the plains or 

 low countries. 



"3. There exist in Europe, without counting certain small 

 continental or insular centres, three great centres of creation : 

 1. The Spanish centre. 2. The Alpine centre. 3. The Tau- 

 rian centre. 



"4. The species which are distributed throughout the whole 

 European system originate in these centres. 



" 5. Each centre possesses a peculiar fauna, entirely special, 

 and composed of a series of adapted types. 



" 6. To the north of these centres the area of the species is 



