Distribution of Moths of the Sub-family Bistonince. 315 



the European contingent. Quite the larger portion of its 

 Pliocene habitats were north Asiatic, and these it enjoyed 

 long after the European detachment had been driven back. 

 Even in Siberia, however, the land in time became ice-bound, 

 and it was only in maritime districts and sheltered nooks in 

 non-glaciated mountains that survival was possible. There 

 it persisted but, ere encroachment on lands where once the 

 ice held sway was feasible, Japan was severed from the main- 

 land and insular, as opposed to conditions almost continental, 

 played their part. As a result of such determining factors 

 added to geographical isolation, specific divergence occurred, 

 and the Japanese race became P. sinulosaria. Not far away 

 mutation was working too, and the slimmer P. (?) verecundaria 

 appeared. 



Subject to no such novel conditions, but still influenced by 

 its environment to some extent, the continental division 

 diverged so very slightly that its divergence was of varietal 

 value only, and has resulted in the Siberian local race extinc- 

 taria. 



When a more temperate climate was once again the 

 possession of Siberia, a gradual westward movement ensued, 

 resulting in the occupation of all the other stations of the 

 present day. 



XIII.— THE GENUS CONIODES (HULST). 



Coniodes plumigeraria (Hulst). Distribution : — British 

 Columbia, California and Colorado. 



We often hear it propounded as a paradox that, whilst the 

 Flora and Fauna of Atlantic North America seem to contain 

 the same general elements as that of Pacific Asia and Japan, 

 on the contrary the affinities of the Flora and Fauna of Pacific 

 America are more or less with those of Europe. 



For practical purposes, the former statement may be 

 regarded as strictly in accord with the facts, because both 

 areas in question include within their limits the remains of a 

 Fauna and Flora which was once universal in the Northern 

 Hemisphere as was pointed out in discussing the genus Am- 

 phidasys. Differences of detail, involving the presence of 

 ' representative ' species, occur, but these in themselves are 

 insufficient to alter the facies of the life of the two regions. 



The latter portion of the paradox is only relatively true. 

 As was mentioned in studying the Mid-Tertiary genus Am- 

 phidasys, compared with Eastern North America, the area west 

 of the Rockies is, geologically speaking, young. Naturally, 

 therefore, the old Tertiary plants and animals, except those 

 which could cross the plains or had fled down the mountains 

 themselves were not able, except at isolated points, to reach 



1917 Oct. 1. 



