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 Perzpatus 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 Perzpatus 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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