$8 HISTORY OF THE EUROPEAN FAUNA. 



between the Caucasus and the Crimea became 

 interrupted. The latter existed for a long time as 

 an island, and only much later, in recent geological 

 times, did it become united with Southern Russia' 

 by means of the isthmus of Perekop." 



There is, on the whole, a great diversity of opinion 

 as to how the European fauna has originated ; how- 

 ever, except in Dr. Kobelt's work, no attempt has 

 hitherto been made to collect together all the available 

 information, and to include in the inquiry more than 

 one class of animals. The little work which I venture 

 to bring before the public will not by any means ex- 

 haust the subject, nor is our knowledge of the Euro- 

 pean fauna sufficient to give more than a mere sketch 

 of many of the animal groups mentioned. As we 

 have learned in the introduction, different classes of 

 animals are not all of equal importance in indicating 

 the changes which have taken place in the distribution 

 of land and water. While Dr. Kobelt is of opinion 

 that the land-snails are by far the most important 

 in such an inquiry, Mr. Lydekker believes that 

 mammals afford the safest and truest indications 

 of such changes. Mr. Beddard puts in a claim for 

 earthworms, as even a narrow strait of sea-water 

 forms an insuperable barrier to their dispersion. 

 Dr. Wallace agrees with Mr. Lydekker, and goes 

 so far as to say (p. 74) that " whenever we find 

 that a considerable number of the mammals of two 

 countries exhibit distinct marks of relationship, we 

 may be sure that an actual land-connection, or at 



