Over a South Atlantic Continent 441 



been found in Europe and N. America, are truly marsupial, 

 — a conclusion that is still open to question — the ancestors 

 of the bearers of these might well have spread from 

 Europe into America, or in reverse relation, by early Cre- 

 taceous times. But the writer would postulate that, as 

 with many plants and invertebrate animals, a great migra- 

 tion southward from N. America into S. America took 

 place in late Jurassic or early Cretaceous times, also then 

 and later a great extension of Jurassic-Cretaceous types of 

 plant and animal was effected over N. America. And so 

 far as present evidence goes, the marsupial family Didel- 

 phidae may have evolved during mid or late Cretaceous 

 times in Central or South America, along with Prothyla- 

 cinus and other polyprotodont marsupials. The Didel- 

 phidae, spreading into North America and thence across 

 North Atlantis into Europe, could well have existed there 

 in Eocene time, and have left those Oligocene opossum 

 remains that have been found there. 



But during late Cretaceous and early Eocene times, a 

 more and more extensive connection was made from temper- 

 ate South America to Southern Atlantis or even to — what 

 we now know to have definitely existed — the climatically 

 favorable Antarctica. Along this southern land polyproto- 

 dont and evolving diprotodont marsupials evidently trav- 

 elled, side by side with plants, earthworms like Acantho- 

 drilus, and other groups to be recorded. Early contact was 

 evidently made, probably in the Eocene period, with Tas- 

 mania and south-east Australia. Along the eastern side of 

 Australia marsupials must have multiplied and varied rap- 

 idly, till they reached and passed along a short-lived and 

 probably early Miocene land-bridge that connected Cape 

 York and Eastern New Guinea with some of the East In- 

 dian Islands. This accordingly became the most northern 

 area for marsupial invasion of Asia. 



If we turn however to other vertebrate groups; an 

 amphibian series that strikingly confirms Forbes' contention 

 is that of the Cystignathous Frogs. These consist of about 

 18 genera, distributed mainly from Central America to 

 western S. America, with a few eastern outliers; also of 

 8 genera that extend over eastern and central Australia. 



