MAMMALIA OF THE SANTA CRUZ BEDS. 
PART I. TYPOTIIER1A. 
BY 
WILLIAM J. SINCLAIR, 
Princeton University. 
INTRODUCTION. 
P ERHAPS no element in the Santa Cruz fauna has been less under- 
stood, or has given rise to more phylogenetic speculation than the 
Typotheria. These animals form a comparatively small part of the 
total fauna, only four genera occurring in the Santa Cruz formation, but 
what they lack in generic and specific diversity they make up in the 
abundance of individuals. Considerable variation, apparently individual 
in character, is observable and, with the fragmentary material hitherto 
available, it is not surprising that the number of species has been inordi- 
nately increased, no less than fifty-one being listed from the Santa Cruz 
alone. 
Professor W. B. Scott has most generously placed at the writer’s dis- 
posal for study and description the large collection of Santa Cruz Typo- 
theria brought together in the museum of Princeton University by Messrs. 
Hatcher and Peterson. The writer is further indebted to him not only 
for many helpful suggestions, but for the use of notes and photographs 
of type specimens in the Ameghino collection. Through the kindness of 
Professor Henry F. Osborn it has been possible to study in connection 
with the Princeton material the Santa Cruz Typotheria of the American 
Museum of Natural History. A collection obtained from Dr. Ameghino 
of Buenos Aires, Argentina, by the Akademie der Wissenschaften at 
Munich, accompanied by his original manuscript labels, access to which 
was kindly permitted by Dr. F. Broili and Dr. Max Schlosser, has been 
especially valuable in working out the synonymy adopted. 
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