These animals, being few in number and wholly confined to the tropical and sub-tropical regions, are of comparatively little interest as regards geographical distribution. America possesses both Crocodiles and Alligators; India, Crocodiles and Gavials; while Africa has Crocodiles only. Both Crocodiles 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 number 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.—TESTUDINIDÆ. (14 Genera, 126 Species.)
| General Distribution. | |||||
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| Neotropical Sub-regions. | Nearctic Sub-regions. | Palæarctic Sub-regions. | Ethiopian Sub-regions. | Oriental Sub-regions. | Australian Sub-regions. |
| 1. 2. 3. 4 | 1. 2. 3. 4 | 1. 2 — 4 | 1. 2. 3. 4 | 1. 2. 3. 4 | 1 — — — |
The Testudinidæ, 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 Neotropical and Oriental regions; in the Ethiopian there is a considerable diminution in the number of species, and in the Palæarctic they are still less numerous, being confined to the warmer parts of it, except one species which extends as far north as Hungary and Prussia. The genera are:—
Testudo (25 sp.), most abundant in the Ethiopian region, but also extending over the Oriental region, into South Europe, and the Eastern States of North America; Emys (64 sp.), abundant in North America and over the whole Oriental region, less so in the Neotropical and the Palæarctic regions; Cinosternon (13 sp.), United States and California, and Tropical America; Aromochelys (4 sp.), confined to the Eastern States of North America; Staurotypus (2 sp.), Guatemala and Mexico; Chelydra (1 sp.), Canada to Louisiana; Claudius (1 sp.), Mexico; Dermatemys (3 sp.), South America, Guatemala, and Yucatan; Terrapene (4 sp.), Maine to Mexico, Sumatra to New Guinea, Shanghae and Formosa—a doubtfully natural group; Cinyxis (3 sp.), Pyxis (1 sp.), Chersina (4 sp.), are all Ethiopian; Dumerilia (1 sp.), is from Madagascar only.
Family 58.—CHELYDIDÆ. (10 Genera, 44 Species.)
| General Distribution. | |||||
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| Neotropical Sub-regions. | Nearctic Sub-regions. | Palæarctic Sub-regions. | Ethiopian Sub-regions. | Oriental Sub-regions. | Australian Sub-regions. |
| — 2 — — | — — — — | — — — — | 1. 2. 3. 4 | — — — — | — 2 — — |