Bd VI: 4) 
THE ECHINOIDEA. 
IOI 
tinent), as it may be concluded that such a land connection would have left its traces 
in the littoral fauna (as well as in the land fauna and flora) — or as IHERING says: 
»Identische Küstenspezies weisen auf ehemalige Zusammenhang der Küsten him 
(»Archhelenis und Archinotis» 1907, p. 185), a sentence which I can adopt with the 
modification, that such species should not have pelagic larvæ and not be capable of 
being transported on floating algæ. 
It is, of course, impossible from the study of the Echinoid fauna alone to prove 
anything about a connection between these regions in very remote periods, palaeo- 
zoic or elder mesozoic. But it is possible to fix the period beyond which such a 
connection cannot have existed. It is to be noticed that such characteristic forms as 
Protocentrotus , Spatangus and Echinocardium are not known from South America, 
recent or fossil. Since the two latter, at least, are well developed in the Eocene, 
it seems justifiable to conclude that a connection between South America, South Africa 
and New Zealand cannot have continued beyond the Cretaceous period. It is like- 
wise to be concluded from the characteristic Echinoid family, the Temnopleuridæ , 
so richly developed in the Indo-Pacific region but totally wanting at the American 
coast, that the supposed connection between South America and the Australian re- 
gion (Chili, New Guinea, New Zealand) cannot either have continued beyond the 
Cretaceous period, since the Temnopleurids are already well developed in the Eo- 
cene period. 
In addition to the above zoogeographical remarks on the South American 
Echinoid fauna I would take the occasion here to give some further notes on a few 
zoogeographical questions, pointing out what may be concluded from the littoral 
Echinoid fauna of this region, whose importance in zoogeography has been made so 
evident especially through the researches of Professor H. v. IHERING. 
It should first be pointed out that the very great percentage of endemic forms 
among the Echinoids of the Patagonian region is a fact perfectly in accordance with 
the »Archiplata»-theory of IHERING, according to which this part of South America 
is zoogeographically distinct from the more northern parts, »Archiguiana» and »Archi- 
brasil», which latter are maintained to have been in connection with Africa in the 
Eocene period. The Echinoidea of the Patagonian region bear evidence of having 
developed here along the coasts of a large tract of land, isolated from Brasil. This 
isolation would be very perfectly realised through the land connection with Africa, 
as is sketched by IHERING in the map accompanying his book »Archhelenis und 
Archinotis». — It may be wondered why these species have not now passed over to the 
Brazilian coast, though these coasts are now in direct continuation. I would suggest 
that the reason is mainly the La Plata river, its immense mouth forming, with its 
fresh or brackish water, an almost insuperable hindrance for their wandering to- 
wards the North. According to IHERING the Rio Negro forms the boundary between 
