PDF - Wallace Online

CHAP. XIX.] REPTILES. 407
little interest as regards geographical distribution. America
possesses both Crocodiles and Alligators; India, Crocodiles
and Gavials ; while Africa has Crocodiles only. Both Croco-
diles and Gavials are found in the northern part of the
Australian region, so that neither of the three families are
restricted to a single region.
Fossil Crocodilia,
The existing families of the order date back to the
Eocene period in Europe, and the Cretaceous in North
America. In the south of England, Alligators, Gavials
and Crocodiles, all occur in Eocene beds, indicating that the
present distribution of these families is the result of partial
extinction, and a gradual restriction of their range—a most
instructive fact, suggesting the true explanation of a large num-
ber of cases of discontinuous distribution which are sometimes
held to prove the former union of lands now divided by the
deepest oceans. In more ancient formations, a number of
Crocodilian remains have been discovered which cannot be
classed in any existing families, and which, therefore, throw no
light on the existing distribution of the group.
Order V.— CHELONIA.
Family 57.—TESTUDINID^. (14 Genera, 126 Species.)
Nfotropical
SirB-REGIONS.
Nearctic
Sub-regions.
General Distribution.
Pal^earctic
sub-iiegion.s.
Ethiopian
SuB-RtGIONS.
Oriental
sob-reoions.
1.2.3.4 11. a. 3. 4 l.a-4.il.2.3.4.1.2.3.4.
Australian
Sub-regions.
The Testudinidse, including the land and many fresh-water
tortoises, are very widely distributed over the Old and New
worlds, but are entirely absent from Australia. They are
especially abundant in the Nearctic region, as far north as
Canada and British Columbia, and almost equally so in the
YoL. II.—27