10 EMYDOSAURIAN AND TESTUDINIAN REPTILES 
The discovery of a fresh-water tortoise, referable to a 
family which has hitherto been regarded as exclusively con- 
fined to the northern and middle portion of the American 
continent, in an island so far removed from its present centre 
of distribution, is most remarkable, and cannot fail to be of 
great interest to all herpetologists. 
With regard to the geographicial distribution of the 
family it is noteworthy that the common American Alligator 
Terrapin (Chelydra serpentina) ranges southward to Ecuador,* 
which State les within about the same parallels of latitude as 
New Guinea. North America being now the acknowledged 
metropolis of the chelydrids, it is interesting to consider by 
what route’ this neogean family travelled round to south- 
eastern New Guinea; and since it has never, so far as I am 
aware, been suggested that there was, at any bygone era of 
the earth’s existence, land communication betwen Papuasia 
and the north-eastern regions of South America, similar 
to that which at two distinct periods undoubtedly existed 
between south-western America, south-eastern Australia, 
and South Africa, the conclusion is irresistibly forced upon us 
that the migration, if migration there were, must have been 
through eastern Asia, though even here we are confronted 
with the problem of its passage from island to island.  Al- 
ternatively it may be held that the Old World was the original 
birthplace of the chelydrids, from whence they spread to the 
New World, and there, having multiplied under the favourable 
conditions of huge marshes and rivers and a scanty and 
nomadic population, exist in numbers even to the presert day 
though practically annihilated elsewhere. And this again 
gives rise to another interesting speculation—whether similar 
or closely related genera may not still survive in the great 
marshes and river systems of the interior of the Chinese 
Empire, a vast territory the biology of which is but little 
understood. This is of course purely conjectural, but many 
important discoveries have had their origin in as small a 
basis of fact, and this suggestion may also be worth investiga- 
tion. But we cannot dismiss the subject of distribution 
without some inquiry into the extinct forms. Like the recent 
*It is also worth mentioning that Mr. Boulenger has recently described 
from Mount Victoria, New Guinea, a frog whose only congener is an indigene 
of Eeuador. 
