372 MOSTLY MAMMALS 
of the eyes is different; while Proscorpius, of the upper 
Silurian rocks of North America, is also of the same general 
type. With Palacophonus of the Silurian of Scotland and 
Gotland, we reach, however, a more primitive type, in which 
the walking-legs gradually taper to thin extremities, termi- 
nating in simple claws or points, although the palpi still 
form large pincers. 
Such is the palaeontological history of scorpions ; and 
very remarkable history it is, seeing that most of the 
Palaeozoic types are almost as highly specialised as their 
existing descendants, and thus show that we should have 
to go much farther back before we reached the ancestral 
type. With the exception of certain cockroach-like insects, 
which occur in the middle Silurian, the scorpions are indeed 
the oldest land animals, and are therefore entitled, in spite 
of their unpleasant propensities, to our utmost respect. 
We have said that in Palaeozoic times there existed a 
south equatorial land-girdle, distinguished from the land 
of the northern hemisphere (from which it was probably 
isolated) by the peculiar character of its flora; and as the 
Palaeozoic scorpions inhabited the northern land, it is 
scarcely likely that they were also found in the southern 
zone. During the Secondary epoch the latter zone appears 
to have been split up, and the continental areas consequently 
assumed some approach to their present configuration. 
The descendants of the ancient Palaeozoic scorpions began 
soon after, in all probability, to migrate southwards, along 
the different lines of communication; and we thus can 
readily understand why some of the existing sub-families 
are represented in such widely separated areas as India, 
Africa, South America, and Australia, without resorting 
to any comparatively recent connection between these 
countries. 
