ORTMANN : TERTIARY INVERTEBRATES. 315 



Finally Osborn (1900, p. 565 and map on p. 566) accepts fully the 

 theory of Antarctica, and, in the main, follows Forbes, although his recon- 

 struction of this old continent by elevation to the 3O4o-meter sounding 

 line is not quite as extensive as that of Forbes. In this respect Osborn's 

 view is intermediate between Forbes' and Hedley's, and decidedly 

 approaches our conception. 



Thus we see that of the various theories advanced for the explanation 

 of the similarity of the southern faunas, the theories of Gill, Wallace, and 

 also the second theory of Hutton have not been considered seriously by 

 subsequent writers, while the oldest one, formulated by Ruetimeyer, has 

 furnished the fundamental idea for them. One of them, Forbes, has- 

 pushed this idea to an extreme, which we cannot accept by any means, 

 while Hedley has attempted to restrict it to reasonable proportions, and 

 to reconcile it with the zoogeographical facts as well as with the present 

 conditions of distribution of land and water in the southern hemisphere. 

 In this sense, Hedley's specification of the Ruetimeyer-Hutton theory is 

 the most conservative, especially as compared with Forbes' fancies, and 

 it is only natural that we should accept his ideas as the most probable of 

 all, that is to say, we accept the first theory of Ruetimeyer and Hutton, 

 with the restrictions put upon it by Hedley. 



For our present purpose, this acceptance of the theory of the former 

 existence of an "Antarctica" means that we are of the opinion that the 

 elements of the fossil Patagonian fauna resembling certain forms in 

 New Zealand and Australia are to be regarded as an additional proof 

 of the former connection of South America with Australia and New Zea- 

 land. Since the respective shells are all preeminently inhabitants of the 

 littoral, of shallow water, and since it is very probable that they were 

 unable to cross over large extents of deep sea, a region of shallow water 

 must have formed a connection between both parts, and nothing is more 

 natural than to assume that this shallow water accompanied the coast line 

 of ancient "Antarctica." It does not necessarily follow that this coast 

 line was a continuous line along the uninterrupted shores of a truly con- 

 tinental mass, but it may have consisted of a chain of islands, at least in 

 part. As Hedley urges, we should not regard the Antarctica as a solid 

 continent, but probably it was broken up at certain times into parts, which 

 were united again in one or another direction. This assumption seems 

 to be chiefly supported by the evidence furnished by land animals, and 

 will be discussed elsewhere in this work. 



