226 R. I. POCOCK [march 



genera Scorpiops, Chaerilus, and Isometrics, and the Pedipalps of the 

 family Thelyplionidae never succeeded in reaching Africa. 



This Pliocene incursion into India took place before the separation 

 of Ceylon. After the occurrence of this event India seems to have 

 been invaded from the north-west, by way of the Punjab and Sind, by 

 its existing genera of Solifugae (Galeodes and Rhagodes (Rkax) ), and by 

 the scorpions of the genera Butheolus and Buthus. These forms occur 

 in abundance in Persia, Arabia, and neighbouring countries, but are 

 absent from Burma and Ceylon. 1 



The similarity between Indo-Ceylon and the Indo-Malaya, so far 

 as scorpions and Thelyplionidae are concerned, proves either a more 

 intimate union between the two than at present obtains, or a common 

 source in the north, whence a simultaneous southward migration into 

 the two areas took place. Since there is no evidence to be drawn from 

 other sources in favour of the former supposition, the latter may be 

 adopted as furnishing an explanation of the facts. In that case we 

 may conceive that the common source was the Siwalik fauna, which; 

 as has been explained, has left mammalian traces in Burma, China, and 

 various parts of Indo-Malaya (Java, Sumatra, the Philippines). 



But whether this be so or not, the extension of the scorpions 

 Hormurus, Isometrus, and Archisometrus, and of Pedipalp Thelyphonus 

 right away from India and Burma, and of Amblypygous Pedipalps of 

 the family Charontidae from Burma to Papuasia, or even North- 

 Eastern Australia, shows that there was at that time no barrier to 

 migration between Indo-Malaya and Austro-Malaya. In this respect 

 the Arachnida offer a striking contrast to the Siwalik mammals, which 

 for the most part did not cross " Wallace's line." 



Nevertheless from the absence of the Pedipalpi and Solifugae from 

 Australia, it seems evident that this continent, with the exception, per- 

 haps, of its north-eastern portion, was separated from the countries lying 

 to the north of it at the time when the Arachnida in question entered 

 Papuasia. Two of the typically Oriental genera of scorpions, namely, 

 Isometrus and Archisometrus, are met with in Australia, it is true ; but 

 with these exceptions, the scorpions of this area are strikingly different 

 from those of the Oriental region. There is one peculiar genus of 

 Buthidae, Isometroides ; a second peculiar genus is Cercoplionius, 

 belonging to the Bothriuridae, a family elsewhere occurring 2 only in 

 South America, where it has many genera and species. A third 

 peculiar genus is Urodacus, the type of a special family or sub-family 

 belonging to the same section of the Order as the Scorpionidae of India, 

 Malaysia, and South Africa. 



1 One species of Rhagodes has been recorded from Ceylon ; but the accuracy of the 

 locality appears to me to be doubtful. 



2 An example of this group has been recorded from Sumatra ; but since the specimen 

 appears to be specifically identical with a form common in the Argentine, there can be 

 little doubt that it was not taken in Sumatra. The opportunity of examining this species 

 I owe to the courtesy of M. Simon. 



