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The Dipsadidae, or Nocturnal Tree Snakes, are distinguished from the last family by their dark colours and nocturnal habits. They are about equally abundant in the Oriental and Neotropical regions, less so in the Ethiopian, while only a single species extends to North Australia. The following are the best known genera :
Dipsas, comprising all the Oriental species with one in AsiaMinor, and a few from the Moluccas, New Guinea, North Australia, West Africa, and Tropical America; Thamnodyastes, Tropidodipsas, and several others, from Tropical America; Dipsadoboa, from West Africa and Tropical America; Leptodeira, from Tropical and South Africa, South America, and Mexico; and Pythonodipsas, from Central Africa.
The Lycodontidae, or Fanged Ground Snakes, are confined to the Ethiopian and Oriental regions, over the whole of which they range, except that they are absent from Madagascar and extend eastward to New Guinea. The genera have often a limited distribution :-
Lycodon ranges from India and Ceylon to China, the Philippines, and New Guinea; Tetragonosoma, the Malay Peninsula and Islands; Leptorhytaon and Ophites, India; Cercaspis, Ceylon; and Cyclocorus, the Philippines. The African genera are Bowdon, Lycophidion, Holuropholis, Simocephalus, and Lamprophis, the latter being found only in South Africa. The species are nearly equally abundant in both regions, but no genus is common to the two.
The Pythonidae, 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; Emygrus is found in the Moluccas, New Guinea and the Fiji Islands; Hortulia is African; Sanzinia is peculiar to Madagascar; Boa, Epicrates, Corallus, Ungalia, and Eumectes 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.