140 THE VICTORIAN NATURALIST. 



bird, declared by Professor March to be a carnivorous swimming 

 ostrich. They are of immense antiquity, and probably their 

 ancestors possessed power of flight. The other birds are in 

 general related to old world fauna. 



Amphibia. — No tailed amphibia. Distribution is at variance 

 with that of the birds. One family is confined to Australia and 

 South America. Two others are absent from North America, but 

 closely allied forms are found in Australia, New Zealand, and 

 South America. 



Fish. — Among freshwater fish the most remarkable is Cera- 

 todus, allied to Lepidosiren of Tropical America, and Protop- 

 terus of fossil Africa. These, like struthious birds, are remains 

 of once widely distributed group. They have both gills and lung. 

 Three groups of freshwater fish are found only in Australia and 

 South America. This is a remarkable affinity between Australia, 

 New Zealand, and South America. 



We have now to consider the barriers that must have been 

 overcome before Australia was stocked with its present fauna and 

 flora. You will remember that the chief types of life originated 

 in the north, and spread southwards, and barriers that terrestrial 

 forms would meet with were ocean, climate, rivers, mountains, 

 and deserts. 



In considering flora we have already dealt with deserts and seas 

 of Australia itself. But by what means did diff"erent forms arrive 

 here in the first instance ? 



Australia is at present an island, but a glance at our i,ooo- 

 fathom line on map shows us a very different contour from the 

 present. I must remind you that the line is supposed to represent 

 the limits within which changes of land and sea have been going 

 on during geological ages, and we see at a glance the probable 

 former connections of Australia with Tasmania, New Zealand, and 

 the Oriental region. When the cretaceous sea divided Western 

 Australia from Eastern, a long, narrow belt of land extended from 

 Cape York, or perhaps from New Guinea, to Tasmania. The 

 western and more ancient land already possessed, in its main 

 features, the peculiar Australian flora and ancestral forms of its 

 strange marsupial fauna, both of which it had probably received 

 by some former union with Asia over the Java Sea. Eastern 

 Australian flora had been derived from three sources — Australian 

 vegetation from across the sea, Polynesian from north and north- 

 east, and south temperate forms from Antarctic land ; and its 

 ancestral struthious birds from New Guinea. New Zealand was 

 now in close connection with North-Eastern Australia, and by 

 this means Australian flora and struthious birds passed. This 

 land connection was broken down before the mammals had 

 passed into Eastern Australia, and later, after passage of mammals 

 and western flora, connection with Tasmania broken. 



