48 HISTORY OF THE EUROPEAN FAUNA. 



chologist is able to make a collection of several 

 hundred different kinds, whilst farther east again they 

 diminish. This clearly indicates there is in South- 

 Eastern Europe a powerful centre of creation of 

 Clausilice, from which the species have spread all 

 over Europe. But it is by no means certain that this 

 centre was always in our continent, for in South- 

 Eastern Asia and the Malay Archipelago Clausilice 

 increase once more. It is interesting to note, however, 

 that almost all these eastern forms belong to the sub- 

 genus Phcedusa (vide Boettger), which had only been 

 known as a fossil genus from a few species in the 

 Eocene and Oligocene of Southern Europe. The 

 first centre of origin, therefore, may possibly have 

 been in Southern Asia, and in these early Tertiary 

 limes a second centre may have become established 

 in Southern Europe from which the sub-genus Gar- 

 nieria went eastward, Macroptychia southward, and 

 Nenia westward across the Atlantis to South America. 

 Only a few remnants of these primitive Clausilicz 

 are now left in Europe, such as the interesting Cl. 

 (Laminifera] Fault. 



As an example of a genus which has its centre of 

 distribution in South-Western Europe we might take 

 that to which our common brown garden slug belongs, 

 viz., Arion. Dr. Simroth, who was the first to point 

 out that the species of Arion had spread over our con- 

 tinent from South-Western Europe (p. 5), is inclined 

 to the belief that the Arionidce had originated on the 

 old land-bridge between Europe and North America. 



