152 
ORIGIN OF LIFE IN AMERICA 
support its being one of the clog tribe (Canidae), we should 
hesitate before accepting the earlier opinion. 
The genus Procyon, to which the North American raccoon 
belongs, only makes its appearance in the Pleistocene Period. 
Nevertheless, it is quite possible that cave deposits, such as 
that described from McCloud River in California containing 
the new specie-s Procyon sinus, may eventually be placed in 
the Pliocene series.* At any rate, the genus Procyon must 
have existed before Pliocene times, and it seems to me prob¬ 
able that it originated either in South America or in some 
western lands which have long since subsided. Dr. von 
Ihering f believes that the Procyonidae have undoubtedly 
come from eastern Asia. Why he should think so I cannot 
imagine, for neither recent nor fossil species are known from 
that continent. 
It is now generally admitted, as I mentioned already 
(p. 95), that Central America assumed its present shape and 
contours at some time during the Pliocene Period (compare 
p. 243). As soon as this land bridge became habitable for 
terrestrial animals, northern species are supposed to have 
poured across it into South America. We possess strong 
evidence certainly that a steady stream of southern animals 
invaded the northern continent in Pliocene and even in 
Pleistocene times and that northern ones succeeded in reach¬ 
ing the south. 
The group of the so-called toothless mammals (Edentata), 
comprising the ant-eaters, sloths and armadillos, are almost 
entirely confined to South America; and that continent no 
doubt is their original home. A few penetrated in some 
mysterious manner to North America in Eocene times, as I 
shall explain more fully in another chapter. Shortly after¬ 
wards they seem to have become extinct again in North 
America, for no traces of edentates have yet been discovered 
in the succeeding Oligocene deposits. It is only in the 
Miocene beds of North America that we again meet with 
examples of this curious group. They were representatives 
of the huge Megalonyx which is closely allied to a southern 
* Gidley, J. W., “ Fossil Raccoon from Californian Cave.” 
t Ihering, H. von, “ Siidamerik. Raubtiere,” p. 160. 
