444 
PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 
dentia. The characters which they possess are in no respect transitional 
to the Multituberculata. The Paucituberculata, like the Sparassodonta, 
are a group founded on a misconception of relationships and should be 
abandoned. 
BEARING OF THE SANTA CRUZ MARSUPIALS ON 
ZOOGEOGRAPHY. 
The reality of a former land connection between the Australian region 
and South America is plainly indicated by several lines of evidence based 
on the distribution of fishes, land shells, decapod crustaceans, plants, and 
Tertiary marine molluscs (Ortmann, 1902). This land connection is be- 
lieved to have existed not later than the close of the Cretaceous or be- 
ginning of the Tertiary, and it is only by such a connection that the 
distribution of the Thylacynidae can be explained. The direction, 
continuity or discontinuity of this land bridge need not enter into the 
present discussion. So far as the Thylacynidae are concerned, there can 
be little doubt of their South American origin, judging from the marked 
adaptive radiation which they attained during the Santa Cruz epoch, but 
whether the same can be said of marsupials in general is still a matter of 
question. It is believed, however, that the order may be properly regarded 
as of southern origin and that the occurrence of opossums in North 
America and Europe may be explained as the result of migration from 
the southern hemisphere. 
MARSUPIALIA INCERTZE SEDIS. 
A large number of Santa Cruz marsupials have been named by Ame- 
ghino and Mercerat, which are not represented in the collections at 
Princeton University and the American Museum of Natural History. 
Many of these have never been figured and are very imperfectly known. 
At present, the writer is not prepared to add to what has been published 
regarding them. The names and full references to the literature are here 
given. 
BORHY.4ENA Ameghino. 
BorhyaENA fera Ameghino. 
Dynannctis fera Amegh.; Revista Argentina, pp. 148-149, fig. 53, 1891. 
Dinamyctis fera (sic) Amegh.; Ibid., p. 314. 
