320 
ORIGIN OF LIFE IN AMERICA 
dridae) are confined to America and New Guinea, the Aglypha, 
a division of the Colubrine snakes, inhabit south-eastern Asia 
and Papuasia, except one genus which is restricted to Central 
America. The pythons are mainly Australian and southern 
Asiatic, but a single species (Loxocemus bicolor) lives in 
southern Mexico. The American land-snail Bulimulus, as 
we have seen, has its nearest relation (Placostylus) in 
Australia and the islands of the western Pacific. The geogra¬ 
phical distribution of the land isopods belonging to the group 
of Spherilloninae, from New Zealand, Australia, Polynesia, 
south-eastern Asia and Japan to south-western North 
America, seemed to Mr. Budde-Lund * so very peculiar that 
he invoked a Pacific continent to explain it. As a matter of fact 
we have very numerous similar instances indicating a striking 
faunistic affinity between North America and eastern Asia. 
But these examples belong to an entirely different category 
from the animals and plants referred to as forming the later 
Asiatic immigration. Certain closely allied or even identical 
forms such as the alligator, the blue-tailed skink and the 
ground-lizard in America and eastern Asia apparently point 
to a geologically recent faunistic interchange between these 
countries. But alligators are known even from the earliest 
Tertiary deposits, while the range of the ground-lizard 
(Lygosoma) from New Zealand, Australia and southern Asia 
as far north as Japan, indicates that the genus is probably of 
Mesozoic origin, and that we have to deal with a remarkably 
persistent ancient type. 
When we take a general survey of the range in North 
America of these older Asiatic animals (and the plants per¬ 
fectly agree with them), we find that their number decreases 
as we go north-westward, but increases towards the south¬ 
west and Central America. The whole stream of these ancient 
Asiatic immigrants seems to have issued forth from the south¬ 
west, precisely from the same part of North America that 
also yielded the European colonists. It is in south-western 
North America, I think, that we have to search for indications 
of the older land connection with Asia, and not in the Bering 
Strait. Another point that strikes us during our general 
Budde-Lund, G., “Revision of Crustacea Isopoda Terr.,” II., p. 40 
