84 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



greatly in their power to cross tho sea, thus land-mammals and 

 batrachians are, as a rule, unable to cross any marine barriers. 

 Mammals, however, can swim further in the sea than batrachians 

 can, the latter and their eggs being killed by sea-water. Snakes are 

 very rarely found in oceanic islands, and those found belong for the 

 most part to particular genera. The occurrence of land-tortoises on 

 what appear to be evidently oceanic islands, such as the Gallipagos, 

 although unexplained, renders the Chelonia less important as evi- 

 dence of land-connexion. Lizards, as a rule, have very small 

 migratory powers across the sea, but some scinques and geckoes 

 appear to form an exception. The powers of dispersal in land- and 

 freshwater mollusca are very limited, though some of them are oc- 

 casionally transported across oceanic barriers. 



It must not be forgotten, too, that when wo wish to inquire into 

 the evidence of Pretertiary land-areas, we must examine as witnesses 

 the descendants of the oldest inhabitants, and must turn for infor- 

 mation to the types that occupied the region before the invading 

 hordes of passerine birds and placental mammals had driven out so 

 many of the aborigines. If we wish to know anything about 

 ancient distribution of land and sea, we must scrupulously ignore 

 the records of a later state of things. Before we can read the old 

 writing on the palimpsest we must clear away all traces of the 

 modern inscription. 



I shall proceed to examine in some little detail (except in the 

 first instance) the evidence of ancient land-connexion : — 



1. Between New Zealand and Australia. 



2. Between the Solomon Islands and New Guinea. 



3. Between Africa and Madagascar. 



4. Between Madagascar and India. 



5. Between South Africa and South America. 



1. New Zealand and Australia. — The question of a former union 

 between New Zealand and Australia has been discussed with great 

 ingenuity in ' Island Life ' by Wallace, who concludes from the 

 geological and biological evidence that New Zealand received its 

 flora and fauna from Eastern Australia at a time when the latter 

 was divided by sea from Western Australia, and that the charac- 

 teristic marsupial and monotreme fauna, with all the peculiar tem- 

 perate flora of Australia, must at the time have been confined to the 

 western island, and consequently did not pass into New Zealand. 



