PART III. MAMMALIA OF THE SANTA CRUZ BEDS. 
MARSUPIALIA. 
BY 
WILLIAM J. SINCLAIR, 
Princeton University. 
INTRODUCTION. 
T HE first descriptions of marsupials peculiar to the Santa Cruz for- 
mation of Patagonia appeared in a brief dissertation by Dr. 
Florentino Ameghino, issued at Buenos Aires in 1887. It soon 
became apparent from the publication of figures in later papers by the 
same author (Amegh., 1889, 1894) that some of these peculiar genera 
resembled closely the pouched wolf or thylacyne of Tasmania, while 
others were more or less like the smaller diprotodont marsupials of Aus- 
tralia, and still others appeared to be related to the opossums of North 
and South America. These resemblances to existing genera, so far as 
could be determined from the figures and descriptions available, were 
confined mainly to the teeth and to the shape of the jaw with its strongly 
inflected angle so characteristic of, although not entirely restricted to, 
marsupials. 
A large amount of material illustrating this group was secured by 
Messrs. Hatcher and Peterson and we are now able, for the first time, to 
ascertain what these animals were like and whether or not they were 
related to existing forms. 
It was originally planned that Mr. Hatcher should contribute this part 
to the series of volumes describing the magnificent collections which his 
energy and devotion to science have brought together in the museum of 
Princeton University. His untimely death necessitated a transfer of the 
work which was to have been his to other hands, and, at the request of 
Professor Scott, it was undertaken by the writer. 
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