I02 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 (Leske) occurs so far south as 5i°35' 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 {Loxechiiius 

 albus, not known outside the Magellan Strait on the Atlantic side) or only from the 

 Atlantic Coast (Ausirocidaris canaliculata, spinulosa, Sterccliinus Agassizii(t), 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. 119.) 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 Loxechiiius albus have spread so slowly, while others, like 

 Arbacia Dufresnii and Notechinus niagellanicus, evidently have spread more 

 quickly. (The Abatus-s-ç(tc\Çi?, 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 difi"ering 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 Échinodermes. 2 sér. II. 1904, p. 21 



