364 NATURAL SCIENCE. May. 1894. 



information we possess regarding comparatively recent fossil Scor- 

 pions is corroborative of this supposition. I refer to the case of a 

 Scorpion described as a Tityus from the amber beds of the Baltic. 

 From this we learn that, in pre-Miocene Tertiary times, Scorpions in 

 Europe reached as far to the north as the 55th parallel, that is, to 

 about the same latitude as the chain of islands which now connects 

 Kamschatka with Alaska. Moreover, although the generic deter- 

 mination of this Scorpion cannot be unreservedly accepted, yet it is 

 highly important to note that, at the present day, in the Old World 

 the only Scorpions which could reasonably be identified as Tityus are 

 found to the south of the tropic of Cancer. It seems, therefore, 

 legitimate to conclude that in pre-Glacial Tertiary times the ancestors 

 of our existing Old World tropical Scorpion fauna extended far enough 

 to the north in the Europaeo-Asiatic continent to pass freely along 

 any land-connection Avith North America. But the advent of glacial 

 conditions in later Tertiary times, and the consequent extermination 

 of the Scorpions in the northern parts of the Northern Hemisphere, 

 would soon put an end to the intercourse between the Asiatic and 

 North American species ; and these, under the changed conditions, 

 might have become differentiated into the distinct types which inhabit 

 these countries at the present day. 



This supposition, then, of the former wide distribution in the 

 Northern Hemisphere of the ancestors of the Ischnuridae and other 

 tropical or sub-tropical families, furnishes, it seems to me, the most 

 satisfactory explanation of the resemblances and differences that are 

 observable between the Scorpions of the Old and New Worlds. 

 Moreover, the restriction of the Diplocentridae and Ischnuridae at the 

 present time in South America to the northern parts of this region 

 points to relatively recent immigration of these groups from North 

 America. In fact, it seems probable that they made their way into 

 the country at a time when it was occupied by ancestors of the 

 existing Neotropical Bothriuridae and Buthidae ; and this last con- 

 clusion points to the further one that these latter two families belong 

 to an older type than the two before-mentioned groups, which are 

 nearly related to the Scorpionidae. This hypothesis, too, is borne out 

 by the confinement of the Bothriuridae in the Eastern Hemisphere to 

 Sumatra and Australia, and by the fact that, although the Buthidae 

 are cosmopolitan in their range, yet peculiar genera of the family are 

 found in South Africa, Madagascar, Ceylon, Australia, and South 

 America. 



R. I. POCOCK. 



