vi] DISTRIBUTION OF SELECTED GROUPS 93 



SCORPIONS. 



This group is a good illustration of the effect of 

 great antiquity. Scorpions already existed in the 

 Silurian, and even some existing species date back 

 to the Coal-measures ! They have had every chance 

 of spreading widely. A species of Tityus is preserved 

 in Miocene amber of the Baltic ; this genus is now 

 restricted to southern South America. The group 

 is cosmopolitan, limited only by cold, yet it is absent 

 from New Zealand. They show scarcely any generic 

 affinity between the Old World and the New, nor 

 between South America and Australia. They have 

 had sufficient time to develop along lines aloof from 

 each other in these great land complexes. 



FISHES. 



Eels are cosmopolitan ; those which live in rivers 

 must descend into deep seas to breed. For some 

 reason the Black Sea is a closed sea to eels, conse- 

 quently there are none in that large part of Middle 

 and Eastern Europe which drains into this sea. Nor 

 are there any in the Volga basin, although this con- 

 tains a sturgeon. 



Pikes (Esocidae), a small well-defined family of 

 freshwater fishes, with only two genera. Esox occurs 

 first in European Oligocene. E. Indus, the common 

 pike, inhabits Europe, excluding Spain, Siberia and a 



