224 



R. I. rOCOCK [makch 



General conclusions concerning the Distribution of the Scorpions, 

 Pedipalpi, and Solifugae. 



The available evidence indicates that the Scorpions and Pedipalpi 

 originated in early Palaeozoic times (the Solifugae perhaps later) in 

 the northern hemisphere, and enjoyed a wide range throughout this 

 portion of the globe, migrating from the eastern to the western side, 

 or rice versd, by a land connection across what is now the North 

 Pacific or North Atlantic, possibly by both routes. Their absence at 

 the present day from the whole of the extensive areas that lie to the 

 north of the 40th or 45th parallels of North latitude, is probably to 

 be attributed to the refrigeration of the northern hemisphere during 

 the glacial epoch. 



If this view of their northern origin be correct, these Arachnida 

 must have migrated southwards into the southern lands they now 

 inhabit ; but since their palaeontology furnishes no help in determining 

 the dates of their migrations, it is necessary to appeal to the evidence 

 supplied by the Vertebrata, and especially the Mammalia, with regard 

 to the past history of the southern continents. 1 



It is considered probable that the ancestors of the existing Afro- 

 Mascarene Mammals fauna entered the Ethiopian region some time during 

 the Oligocene period, when Madagascar was united to South Africa ; that 

 during Pliocene times Madagascar was separated from the mainland, 

 and a more intimate union between Africa and Asia, by way of Syria 

 or Arabia, admitted the more highly organised ancestors of the existing 

 ungulates, monke) T s, etc., which were thus cut off from Madagascar by 

 the Mozambique channel. 



The fact that scorpions belonging to the Buthidae and Ischnuridae, 

 allied to but distinct from the African species, occur in Madagascar, 

 shows that, like the lemurs and the viverrines in the case of the 

 Mammals, representatives of these families inhabited South Africa 

 before the submergence of the land connecting it with Madagascar. 

 Similarly, the absence from this island of the Amblypygous Pedipalpi, 

 of the Solifugae, and of all the African genera of Buthidae and Scor- 

 pionidae, points to the conclusion that these forms entered Africa after 

 the separation of Madagascar. Thus, so far as these Arachnida are 

 concerned, the scorpions were the pioneers in taking possession of 

 Africa. 



There is no evidence against the hypothesis that these incursions 

 synchronised with those of the Mammalia. On account of the very 

 <?reat antiquity of the scorpions, as compared with the Mammalia, it 

 might be considered probable that the former anticipated the latter 

 in their southward movement into Africa. But, it must be remem- 

 bered, there is no evidence that scorpions of the kind found in the 



1 In this connection I have specially consulted Mr. Lydekker's "A Geographical 

 History of Mammals. Cambridge, 1896." 



