Prof. K. A. von Zittel—On the Mammalia. 457 
now existing in Argentina, which according to Ameghino only 
contains 107 species, and it is in this point of view equally com- 
parable with that of the Upper Hocene of Europe. Ameghino 
increases the list further by three alleged Amblypoda (Planodus, 
Adelotherium, Adrastotherium) and a Tillodont (Entocasmus), but 
these additions are based on remains which absolutely do not permit 
of satisfactory determination. In comparison with the Huropeo- 
American Hocene fauna, the complete absence of the Artiodactyla, 
Insectivora, Chiroptera, Carnivora and Prosimiz, is very striking. 
‘The Perissodactyla are represented by two entirely novel extinct 
families (Proterotheride and Macrauchenide) ; the Rodents entirely 
by Hystricomorphous forms of a specifically South American type, 
and equally so the Primates by the Platyrhine Apes. The fauna 
is mainly composed of Marsupials, Hdentates, Toxodonts and 
Typotheria. Only South America possesses representatives of these 
two last orders, which make their appearance in the Santa Cruz 
formation and become extinct in the Pampas formation. Also all 
the forms of Edentates belong to the Xenarthra, which now live 
exclusively in South America, and amongst the Marsupials, the most 
prominent are the Didelphyidew, which still live all over America 
and in the Tertiary period were distributed over the Northern 
hemisphere, but these are accompanied by other forms of the same 
order which show an Australian stamp. Ameghino has placed these 
in part with the Dasyuride and in part with the Creodontia, but as 
regards the last he is now himself doubtful, and acknowledges’ that 
a part at least of the supposed Creodontia may belong to the 
Marsupials. The same may be said of the supposed Plagiaulacide, 
on which Ameghino had mainly relied to determine the age of the 
Santa Cruz formation.? These also probably form an independent 
family of Marsupials, either indigenous or possibly migrated from 
Australia. 
Under any circumstances South America must be considered as an 
independent “centre of creation,” which possibly at an early period 
had been ingrafted from Australia, but which already in the Santa 
Cruz formation had produced peculiar forms of Marsupials. In 
favour of a connection with the mammalian fauna inhabiting Hurope 
and North America at the same time, there is, in spite of the assur- 
ances of Ameghino, no ground of support. On the other hand it 
cannot be denied that there is some authority for the supposition of 
Thering, based on the distribution of the fresh-water animals, that 
South America, during the Mesozoic and Older Tertiary periods, was 
connected by land with Australia and South Africa. The associated 
1 Revista Argentina, I. p. 314. 
2 The examination of a great number of lower jaws and detached teeth of the 
genera Abderites, Acdestis and Hpanorthus, which I owe to the kindness of Senor 
Ameghino, shows that the molars in these genera do not agree, either in number or in 
form, with those of Neoplagiaulax. They greatly resemble those of the Australian 
Hypsiprymnide, and they are proved to be genuine Marsupials by the incurved angle 
of the lower jaws. Ameghino also acknowledges them (Revue génér. des Sciences, 
18938, p. 77) as Diprotodont Marsupials, to which he also further assigns Plagiaulaz, 
Neoplagiaulax and Ptilodus. 
