442 Transactions. — Miscellaneous. 



South American continent has existed only since the OHgocene 

 period. It then consisted of two parts, united by the narrow 

 isthmus of the Andes, which were completely separated from 

 one another before the Oligocene period. These two parts 

 form x\rchiplata (the area occupied at present by Chile, Argen- 

 tina, Uruguay, aiid South Brazil) and Archiguyana (comprising 

 the high plateau of Venezuela and Guyana). Each of these 

 territories had its own fauna and flora, which differed as much 

 from one another as those of interior Africa and North America 

 do at the present time. Archiguyana must have been united 

 with Africa by a land-bridge, a remnant of which is repre- 

 sented by St. Helena, whilst Archiplata extended to the south 

 in a South Pacific Antarctic continent, which during the whole 

 of Mesozoic times kept this area in communication wnth the 

 Pacific continent, from which first a number of Polynesian 

 Islands, then New Zealand, and finally Australia and New 

 Guinea became separated. Eeserved for further investigation 

 remain the questions : Did the Atlantis reach only Archi- 

 guyana, or was a southern arm directed to that part of Brazil 

 which extends between Rio, Bahia, and the Eio S. Fran- 

 cisco? What was its relation to the West Indies'? What 

 age is to be attributed to these parts of Brazil and 

 Archiguyana? Were the mountains of the Brazilian coast 

 also upheaved only during Tertiary times ? — as I presume. 

 All these questions have yet to be examined, as well as the 

 original participation of each of these parts in that mixed 

 fauna and flora which we call now " South American." 



A great deal remains unsolved, but the results obtained re- 

 garding Archiplata and its connection with the Antarctic con- 

 tinent seem to me to be an important acquisition. That Archi- 

 plata owned an old common flora and fresh-water fauna ; that 

 the upheaval of the x\ndes, beginning at the end of the Creta- 

 ceous or commencement of the Eocene period, ending at and 

 after the Tertiary era (in the place of a Jura sea entering with 

 a gulf southwards into Archiplata), formed a barrier which the 

 Tertiary fresh-water fauna migrating to Archiplata could not 

 cross — this essential result of my studies of the fresh- water 

 fauna gives, in my opinion, a very simple and new explanation 

 of a large number of facts, otherwise unintelligible, regarding 

 the geographical distribution of South America's flora and 

 fauna. 



These being the results to which, relative to South America, 

 zoogeography and geology are leading, I, on the other side, 

 believe that the North American scientists are able to bring in 

 accord with this their own experiences. Heilprin''' has inves- 



* A. Heilprin, "The Geograiihical and Geological Distribution of 

 Animals," London (1887), p. ^10. 



