The Pythonidæ, comprising the Rock Snakes, Pythons, and Boas, are confined to the tropics, with the exception of one species in California. They are very abundant in the Neotropical region, where nearly half the known species occur; the Australian region comes next, while the Oriental is the least prolific in these large serpents. The genera which have been described are very numerous, but they are by no means well defined. The following are the most important:—

Python is confined to the Oriental region; Morelia, Liasis, and Nardoa are Australian and Papuan; Enygrus is found in the Moluccas, New Guinea and the Fiji Islands; Hortulia is African; Sanzinia is peculiar to Madagascar; Boa, Epicrates, Corallus, Ungalia, and Eunectes are Tropical American; Chilabothrus is peculiar to Jamaica and Mexico; and Lichanotus to California.

An extinct species belonging to this family has been found in the Brown-coal formation of Germany, of Miocene age.

Family 18.—ERYCIDÆ. (3 Genera, 6 Species.)

General Distribution.
Neotropical
Sub-regions.		Nearctic
Sub-regions.		Palæarctic
Sub-regions.		Ethiopian
Sub-regions.		Oriental
Sub-regions.		Australian
Sub-regions.
— — — —— — — —— 2 — —— 2 — —1 — 3 —— — — —

The Erycidæ, or Land Snakes, form a small but natural family, chiefly found in the desert zone on the confines of the Palæarctic, Oriental, and Ethiopian regions. They range from South Europe to West Africa and to Sikhim. The three genera are distributed as follows:—

Cursoria (1 sp.), Afghanistan; Gongylophis (1 sp.), India and Sikhim; Eryx (4 sp.), has the range of the entire family.

Family 19.—ACROCHORDIDÆ. (2 Genera, 3 Species)

General Distribution.
Neotropical
Sub-regions.		Nearctic
Sub-regions.		Palæarctic
Sub-regions.		Ethiopian
Sub-regions.		Oriental
Sub-regions.		Australian
Sub-regions.
— — — —— — — —— — — —— — — —— 2 — 41 — — —

The Acrochordidæ, or Wart Snakes, form a small and isolated group, found only in two sub-divisions of the Oriental region—the South Indian and the Malayan, and in New Guinea.