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 Palaeophonus 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. 



