SCORPIONS AND THEIR ANTIQUITY 369 



are closely related to the ancestral stock of insects, spiders 

 and their allies, and myriapods. This being so, it is evident 

 that Peripatus must be an extremely ancient type, and there 

 is a great probability that if their remains were suitable for 

 preservation we should find evidence of their existence in 

 some of the oldest rocks of the northern hemisphere. It 

 has, indeed, been assumed from their present geographical 

 distribution that these, as well as many other types of 

 animals, have always been southern forms, and that their 

 presence in the great southern continents and islands 

 indicates a former union of all the lands of the southern 

 hemisphere. That there was a south equatorial belt of 

 land in Palaeozoic times seems to be pretty evident from 

 certain peculiarities connected with the Carboniferous floras 

 of the northern and southern hemispheres, and it is, there- 

 fore, possible that in the case of Peripatus such an explana- 

 tion may be the true one. Since, however, palaeontology 

 teaches us that many ancient types have migrated from 

 their original northern home to find a refuge in the remote 

 parts of the southern continents and islands, it seems more 

 probable that such has also been the case with Peripatus. 

 And if we can show that this has been the case with the 

 scorpions, which now attain their maximum development 

 in the more southern portions of the globe, the argument 

 will be strengthened in the case of Peripatus. 



Belonging to the great group of Arachnida, which includes 

 the spiders, scorpions are especially distinguished by their 

 compressed bodies, and by the sharp separation of the 

 cephalo-thorax from the abdomen, the latter consisting of 

 seven segments, and being followed by six narrower seg- 

 ments, collectively forming the post-abdomen, the last of 

 which is specially modified into the so-called sting. The 

 cephalo-thorax or fore part of the body is covered by a 



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