1893.] Fossil Mammalia of Southern Patagonia, 439 
NEW DISCOVERIES OF FOSSIL MAMMALIA OF 
SOUTHERN PATAGONIA. 
By FLORENTINO AMEGHINO.' 
I. 
At this time, the most important discovery in South Amer- 
ican paleontology is the presence of true monkeys in the 
Eocene of Patagonia. Certain paleontologists have expressed 
doubts as to the age of the remains. I believe that these 
doubts have no foundation from whatever point of view one 
approaches the subject. 
From the geological standpoint, the latest researches of my 
brother, Carlos Ameghino, show that the marine formation, 
which I have named Subpatagonian, and the formation of 
sub-aerial or terrestrial origin that I have designated Santa- 
cruzian (the formation which contains the mammals in ques- 
tion), are conformable without a break. The characteristic 
fossil of Subpatagonian formation is Ostrea bowrgeoisii (R. de 
C.). In the east, toward the Atlantic, the lower part of the 
Santacruzian formation, is found to be intersected with beds of 
Ostrea bourgeoisii, representing the upper part of the Subpata- 
gonian with all the beds of the two formations resting upon 
each other conformably. In the west, toward the Andes, in 
the lower reaches of the Rio Sehuen, and in the vicinity of 
the lakes Viedrua and Saint-Martin, the marine beds of the 
Subpatagonian formation rest on the Dinosaurian beds of 
terrestrial origin, contemporary with the North American 
Laramie (Pehuenche formation) ; the transition from one for- 
mation to the other is almost imperceptible. Throughout this 
region no mammalian remains have been found in any forma- 
tion more recent than the Santacruzian. It is then certain 
that the fossil monkeys belong to this formation. The Ho- 
munculus specimens have always been found in place, and in the 
lower Santacruzian beds.; It is beyond a doubt that the fos- 
sil monkeys belong to the Santacruzian fauna. 
1 From the Revue Scientifique, Jan. 7, 1893. 
