1896.] . Geology and Paleontology. 939 
reduction of a still more complex molar. Most of the evidence for this 
conclusion is derived from the fact, as he believes, that the Mammalia 
of Eocene and possibly earlier age, which are found in Argentina gener- 
ally, have quadritubercular molars. In accordance with this view 
Cetacea and Edentata with numerous ea present a primitive typeof 
dentition which has survive 
The reply which can be made to this fundamental proposition as to 
time-order, is, that M. Ameghino has probably affixed too great an age 
to his earlier beds. This is the opinion of Lydekker, and such extinct 
types as occur in those beds which occur elsewhere confirm this con- 
clusion, Thus the Patagonian, which Ameghino regards as an Eocene 
formation, containing the Pyrotherium, contains also the primitive 
monkeys Anthropops, and the cetaceous Prosqualodon, Argyrocetus 
and Diaphorocetus. Now Diaphorocetus and forms closely allied to 
Arygocetus and Prosqualodon are characteristic of the middle Miocene 
in North America and Europe. . It is highly improbable that the 
quadrumanous genera discovered by Ameghino are of Eocene age, since 
nothing of the kind occurs in Eocene beds in the Northern Hemisphere, 
where more primitive and ancestral lemuroid families represent them. 
The presence of supposed Condylarthra (not yet described) however, 
gives an Eocene character, and if the forms described by Ameghino as 
Multituberculata are really such, this character would be difficult to 
deny. However, recently Ameghino has recognized that these forms do 
do not belong to that order, but are true Marsupialia, and Lydekker 
assert that they do not belong to the Patagonian formation, but to the 
overlying Santa Cruz beds. But supposing that the Patagonian forma- 
tion is upper Eocene, it does not furnish the material for an elucidation 
of the dental characters of the primitive Mammalia. These are only 
partly displayed in the lower Eocene, for it is in the Postcretaceous 
(Puerco and Laramie) that the true ancestral relation of the trituber- 
cular molar is fully seen. These formations may be represented by the 
lower or dinosaurian beds which lie below the Patagonian formation in 
Argentina, but no Mammalian remains have been found there thus far 
by Ameghino. The oldest Mammal is said to be the Pyrotherium of the 
Patagonian formation, but it has an aspect more modern than Eocene. 
It is suspected by Ameghino to be a proboscidian, but it has not yet 
been shown that it is not a marsupial. 
Dr. Ameghino misinterprets North American fossils in more than 
one instance. He cites the Amblypoda in evidence of the proposition 
. that the tritubercular molar is the result of a reduction of the quadri- 
6 Geographical History of Mammals, 1896, 115. Ameghino makes the same 
statement in Enum. Synopt. Mamm. Foss. Eocene de Patagonie, 1894, p. 10. 
