102 
TH. MORTENSEN, 
(Schwed. Südpolar-Exp. 
Archiplata and Archibrasil. As far as I am aware, none of the Patagonian Echi- 
noids, however, are known to occur to the North of La Plata; but careful researches 
on the Echinoid fauna of this region are very much needed, and the present negative 
evidences are to be used with all reservation. It can only be stated that the facts 
known as yet point towards the conclusions drawn here. — - The fact that Encope 
emarginata (Leslie) occurs so far south as 5L35' S. (Rio Gallegos)* indicates a 
wandering in the opposite direction, this species having its home in the West Indian 
region; it must then evidently have passed the La Plata river. (It has not been re- 
corded as fossil from Patagonia, so far as I am aware.) 
Another fact of importance is that some of the species do not pass the Southern 
Extremity of South America, being known only from the Pacific Coast ( Loxechinus 
albus , not known outside the Magellan Strait on the Atlantic side) or only from the 
Atlantic Coast ( Austrocid aris canaliculata , spinulosa , Sterechinus Agassi zii (?), the 
Abatus species). This fact is in accordance with the theory of a former land con- 
nection between South America and the Antarctic Continent. (Also the littoral 
Mollusc-fauna shows the same interesting fact. Cf. IHERING, Archhelenis und Archi- 
notis, p. 1 19.) That these species have not yet passed the Southern Extremity, 
though it does not appear why they could not live on the opposite coast, is, indeed, 
a remarkable fact bearing evidence that some species do not spread very rapidly. 
It would be highly interesting to find out the reason why the two species Austro- 
cidaris canaliculata and Loxechinus albus have spread so slowly, while others, like 
Arbacia Dufresnii and Notechinus magellanicus , evidently have spread more 
quickly. (The Ab atus -s^&c\es may perhaps afford some parallel cases; but on account 
of the confusion previously reigning here, their range, as known at present, is scarcely 
quite reliable. 
It will further be of great interest to see, whether the Echinoid fauna of South 
America bears any evidence for or against the Archhelenis theory, as set forth by 
IHERING. The fact of the Patagonian Echinoid fauna differing so markedly from 
the Brazilian fauna is certainly in favour of this theory; but there is another fact as 
decidedly speaking against it. If there had been in the Eocene epoch such a land con- 
nection as that sketched by IHERING, going from Southern Brazil to Africa, joining 
the recent African Coast from Guinea to the Cape, and even beyond the Cape to the 
Kerguelen group, there would doubtless be a distinct relation between the littoral fauna 
of South Africa and South America. This is, however, at least as regards the Echi- 
noids, decidedly not the case, as I have shown in the »Echinoiden d. deutschen 
Südpolar-Expedition» (p. 98 — 100). The Echinoids, therefore, tend to show that 
there has not been such a direct connection between South Africa and South America 
* De Loriol, Notes pour servir à l’étude des Echinodermes. 2 sér. IL 1904, p. 21. 
