VON Jheking. — On the Ancient Connections of N.Z. 4'i3 



tigated the history of the Laramie region and its lacnstrine de- 

 posits, which attain sometimes a thickness of 4,000ft. to 5,000ft., 

 and show in the beginning an entirely marine character, but 

 change later on to the deposits from fresh water. The drainage 

 was into a continental arm of the sea, which projected com- 

 pletely across the United States during the Cretaceous period, 

 and which prevented an exchange of fresh-water animals 

 between North and South America, as well as the migration of 

 marsupials fi'om Patagonia to the United States. 



The theory of Wallace is not only to be rejected for our 

 special territory of South America, but it is insafticient also 

 for Australia and Polynesia. Wallace thinks that for Poly- 

 nesia the birds are the only group of the animal kingdom " on 

 which we could rely." We should be more in the right if we 

 reverse his sentence and say that the mammals and the birds 

 are the only groups on which no reliance can be put if we wish 

 to unravel the whole history of Polynesia, for birds and 

 placental mammals belong in their recent representatives 

 entirely to the Tertiary era, and therefore cannot be taken 

 into consideration for the means of distribution of organisms 

 during the Secondary era. Moreover, birds are almost useless 

 for the discovery of old geographical land-communications, on 

 account of their power of flight, and on account of the passive 

 migrations to which they may be subject when driven away 

 by the wind. 



Mr. Wallace's explanation of the distribution of the Lacer- 

 tidae through Polynesia as far as the Sandwich Islands by 

 means of a migration across the ocean is just as bold a hypo- 

 thesis as his attempt to explain the occurrence of identical 

 fresh-water fishes in New Zealand and Patagonia by the 

 transport of their fry on icebergs.''' To such theories may 

 those adhere who wish to save Wallace's hypothesis of the 

 stability of the continents and depths of the seas; but one 

 cannot ask unprejudiced scientists to accept such incredible 

 explanations. 



If we look at the circumstances as they really are we 

 perceive that the fauna of Polynesia impoverishes from west 

 to east. A wide distribution is seen only in those groups of 

 animals whose origin does not reach beyond the Tertiary era, 

 which are provided with the power of flight, as birds and bats. 

 Active and passive migration would bring them from island to 

 island, whereby the birds sliow a wider distribution than the 

 bats. If birds fly over the Atlantic Ocean, and accomplish 

 many other distant migrations, then we are really standing 



* It seems much more likely to me that the enormously-wide dis- 

 tribution of pelagic fresh-water Crustacea is due to transporbation by 

 birds. But many of tbem may belong to very old types, living already in 

 Mesozoic lakes, as Limna'Ci and Pliysa did. 



