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 hack 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. — TESTIJDINIDiE, (14 Genera, 126 Species.) 
General Distribution. 
Neotropical 
Sub-regions. 
Nearctic 
Sub-regions. 
PaLjE ARCTIC 
Sub-regions. 
Ethiopian 
Sub-regions. 
Oriental 
Sub-regions. 
Australian 
Sub-regions. 
1 . 2 . 3 . 4 - 
1 
1 . 2 . 3 . 4 - | 
1 . 2 - 4 - | 
1 . 2 . 3 . A 
i 
1 . 2 . 3. 4 
I 
1 
The Testudinidee, 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 ecpially so in the 
