HiNTON — The Fossil Hare of the Ossiferous Fissures of Tghtham. 263 



the group. We may conclude from this that with regard to the organ of 

 sight, L. V. anglicus and L. v. hiheridcus are the least specialized members of 

 the variahilis group ; and we may infer further that both the forms in question 

 are forms which live or liave lived under temperate conditions. 



The limb-skeleton, as we have seen above, gives similar evidence ; for in 

 these two forms of the vanahiUs group, we have the primitive combination of 

 short limbs, and equality of the brachial and ante- brachial lengths. It is 

 true that in the arctic forms of the group short limbs are characteristic, but 

 that this is a secondary specialization or retrogression here is shown by the 

 fact that the radius has become considerably longer than the humerus. The 

 intermediate forms from Scotland and Scandinavia show longer limbs and 

 have rather longer radii than those of the southern forms. 



In these respects, therefore, and in every other point dealt with in the 

 preceding pages, L. v. anglicus and L. v. Jdbernicus distinguish themselves as 

 the two least specialized members of the L. variabilis group, and, on the other 

 hand, the arctic forms are as clearly the most specialized. It is consequently 

 highly improbable tliat the group can have had a boreal origin. Looking 

 at the whole subject broadly, it appears to me to be more likely that the 

 group had its origin somewhere in Central Asia. From this region it later 

 spread eastwards into North America and westwards into Central Europe. 

 The colonization of the high north by the group may have taken place by 

 three distinct routes, viz., (1) directly from Central to Arctic Asia; (2) tlirough 

 North America ; and (3) from Central Europe along the western seaboard 

 through Scotland and Scandinavia. The group has become specialized and 

 differentiated into subspecies in the course of its travels, and particularly as 

 it has proceeded northwards. Therefore the southern forms, living and 

 extinct, remain nearer to the primitive L. variabilis than do the northern 

 ones. 



But if this view brings the distribution of the group into harmony with 

 the structural peculiarities of its members, there yet remains to be explained 

 the singular fact that, with the exception of Ireland, the Z. variabilis group no 

 longer inhabits the plains of temperate Europe. 



In a former paper I have argued that to explain such changes in distribu- 

 tion it is not necessary to invoke great changes of climate.' In the present 

 case the structure of L. v. anglicus itself tends to disprove the idea that the 

 climate of the south of England was any less mild at the time of this Hare's 

 existence there than it is at present. Moreover its nearest ally lives under 



' HiNTON, " On the Existence of the Alpine Vole in Britain during Pleistocene Times," Froo. 

 Geol. Assoc, vol. xs., p. 54. 



