3J-0 ORTMANN — DISTRIBUTION OF DECAPODS [April 5, 



the whole Mesozoic era, but this seems to be doubtful ; at any rate, 

 a connection of the southern and western land in South America 

 (Chilean coast range) with the rest of South America is improbable 

 during a large part of the Cretaceous time, since marine deposits 

 belonging to this period are found in the present Cordilleras, indi- 

 cating separation by sea. This sea apparently was a strait running 

 in a north-southerly direction, and coinciding approximately with 

 the present direction and location of the Cordilleras. This strait 

 became dry at the beginning of the Tertiary, in the Eocene, since 

 Tertiary deposits are not found here, and thus a connection of the 

 main mass of South America, the Brazilian Plateau, was formed in 

 an east-westerly direction with the Chilean coast range. This 

 completed the connection of South America with Antarctica in 

 Eocene times, and, in our opinion, is very important and serves to 

 explain the numerous zoogeographical peculiarities of South 

 America. 



To sum it up, we are justified to draw the following conclusions: 

 There is nothing that opposes, on tectonic or geological grounds, 

 the assumption of a connection of Australia with Antarctica, as far 

 as the evidence at hand goes. This connection belongs pre eminently 

 to the Mesozoic time, and was interrupted, at least for a large part, at 

 the end of this era, definitively at the beginning of the Tertiary. 

 We have no positive evidence for a permanent Mesozoic connection 

 of South America and Antarctica (but such may have existed) ; 

 but a connection of these parts is very probable at the end of the 

 Mesozoic time, and especially during the Eocene between the Antarctic 

 lands and the old Brazilian mass ; the. southernmost parts of South 

 America (southern Patagonia and Chili) were connected in the 

 Cretaceous with Antarctica, forming part of it, but were still 

 separated from Archiplata. In the Eocene they were also con- 

 nected with the latter. This latter union was brought about by 

 the upheaval of the Cordilleras, which began toward the close of 

 the Cretaceous and continued almost all through the Tertiary. 



We are not going to follow up this idea any further, although we 

 believe that it will prove to be very important with regard to the 

 origin of the South American fauna. For our present purpose, the 

 explanation of the presence of the genus Pa^astacus in South 

 America, we arrive at the conclusion that the family Parastacidoz, 

 which existed, as we have seen, during the Upper Cretaceous 

 period in Australia, had a chance, during this same time, to spread 



