The Oligodontidæ are a small family of Ground Snakes which have been separated from the Calamariidæ, and, with the exception of a few species, are confined to the Oriental region. The best characterised genera are:—

Oligodon (12 sp.), India, Ceylon, and Philippines; and, Simotes (24 sp.), India to China and Borneo. In addition to these, Achalinus is founded on a single species from Japan; and Teleolepis consists of three species from North and South America.

Family 7.—COLUBRIDÆ. (50 Genera, 270 Species.)

The Colubrine Snakes are universally distributed over the globe, and they reach the extreme northern limits of the order. They are, however, almost absent from Australia, being there represented only by a few species of Tropidonotus and Coronella in the northern and eastern districts. This great family consists of four divisions or sub-families: the Coronellinæ (20 genera, 100 species), the Colubrinæ (16 genera, 70 species), the Dryadinæ (7 genera, 50 species), and the Natricinæ (7 genera, 50 species). The more important genera of Colubridæ are the following:—

Ablabes, Coronella, Ptyas, Coluber, and Tropidonotus—all have a very wide distribution, but the two last are absent from South America, although Tropidonotus reaches Guatemala; Tomodon, Xenodon, Liopis, Stenorhina, Erythrolampus, Elapochrus, Callirhinus, Enophrys, and Dromicus—are confined to the Neotropical region; Hypsirhynchus, Cryptodacus, Jaltris, and Coloragia, are confined to the West Indian Islands; Chilomeniscus, Conophis, Pituophis, and Ischcognathus, to North America, the latter going as far south as Guatemala; Compsosoma, Zamenis, Zaocys, Atretium, Xenochrophys, and Herpetoreas, are peculiarly Oriental, but Zamenis extends into South Europe; Lytorhynchus, Rhamnophis, Herpetethiops and Grayia, are Ethiopian; Rhinechis is peculiar to Europe; Megablabes to Celebes, and Styporhynchus to Gilolo; Cyclophis, is found in the Oriental region, Japan, and North America; Spilotes, in the Nearctic and Neotropical regions; Xenelaphis in the Oriental, Ethiopian, and Palæarctic regions; Philodryas, Heterodon and Herpetodryas in America and Madagascar, the latter genus being also found in China.

Family 8.—HOMALOPSIDÆ. (24 Genera, 50 Species.)

The Homalopsidæ, or Fresh-water Snakes, have been separated from the Hydridæ by Dr. Günther, and they include some groups which have been usually classed with the Natricinæ. They are especially characteristic of the Oriental region, where considerably more than half the genera and species are found; next comes the Neotropical region which has 6 species; while none of the other regions have more than 4 or 5. It is to be observed that the Ethiopian species occur in West Africa only, and mostly constitute peculiar genera, so that in this family the separation of the Ethiopian and Oriental regions is very well marked. The best characterised genera of the family are the following:—

Cantoria (10 sp.), ranging from Europe to Japan, the Philippines, and Timor, with one species in Guinea; Hypsirhina (6 sp.), Bengal, China, and Borneo; Fordonia (3 sp.), Rangoon to Borneo and Timor; Homalopsis (2 sp.), Cambodja to Java; Cerberus (2 sp.), Ceylon and Siam, the Malay Islands, New Guinea, and North Australia; Herpeton (1 sp.), Siam; Ferania (1 sp.), Bengal to Penang; Pythonopsis (1 sp.), Borneo; Myron (2 sp.), India and North Australia; Homalophis (1 sp.), Borneo; Hipistes (1 sp.), Penang; Xenodermus (1 sp.), Java; Neusterophis and Limnophis, with one species each, are peculiar to West Africa; Helicops (2 sp.), North and South America; Farancia and Dimodes, with one species each, are from New Orleans; and a few others imperfectly known from Tropical America.

Family 9.—PSAMMOPHIDÆ. (5 Genera, 20 Species.)

The Psammophidæ, or Desert Snakes, are a small group characteristic of the Ethiopian and Oriental regions, but more abundant in the former. The distribution of the genera is as follows:—

Psammophis (16 sp.), ranges from West Africa to Persia and Calcutta; Cœlopeltis (1 sp.), North and West Africa; Mimophis (1 sp.), Madagascar; Psammodynastes (2 sp.), Sikhim to Cochin China, Borneo and the Philippine Islands; and Dromophis (1 sp.), Tropical Africa.

Family 10.—RACHIODONTIDÆ. (1 Genus, 2 Species.)

The Rachiodontidæ are a small and very isolated group of snakes of doubtful affinities. The only genus, Dasypeltis (2 sp.), is confined to West and South Africa.

Family 11.—DENDROPHIDÆ. (7 Genera, 35 Species.)

The Dendrophidæ, or Tree Snakes, are found in all the Tropical regions, but are most abundant in the Oriental. The genera are distributed as follows:—

Dendrophis ranges from India and Ceylon to the Pelew Islands and North Australia, and has one species in West Africa; Ahætulla is almost equally divided between Tropical Africa and Tropical America; Gonyosoma ranges from Persia to Java and the Philippines; Chrysopelea is found in India, Borneo, the Philippines, Amboyna, and Mysol; Hapsidrophis and Bucephalus are confined to Tropical Africa; and Ithycyphus (1 sp.), is peculiar to Madagascar.

Family 12.—DRYIOPHIDÆ. (5 Genera, 15 Species.)

The Dryiophidæ, or Whip Snakes, are a very well characterised family of slender, green-coloured, arboreal serpents, found in the three tropical regions but absent from Australia, although they just enter the Australian region in the island of Celebes. In Africa they are confined to the West Coast and Madagascar. The genera are:—

Dryiophis (4 sp.), Tropical America and West Africa; Tropidococcyx (1 sp.), Central India; Tragops (4 sp.), Bengal to China, the Philippines, Java, and Celebes; Passerita (2 sp.), Ceylon and the Indian Peninsula; and Langaha (2 sp.), confined to Madagascar.

Family 13.—DIPSADIDÆ. (11 Genera, 45 Species.)

The Dipsadidæ, 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 Asia-Minor, 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.

Family 14.—SCYTALIDÆ. (3 Genera, 10 Species.)

It is doubtful how far the three genera which constitute this family form a natural assemblage. We can therefore draw no safe conclusions from the peculiarity of their distribution—Scytale and Oxyrhopus being confined to Tropical America; while Hologerrhum inhabits the Philippine Islands.

Family 15.—LYCODONTIDÆ. (11 Genera, 35 Species.)

The Lycodontidæ, 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 Boædon, 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.

Family 16.—AMBLYCEPHALIDÆ. (5 Genera, 12 Species.)

The Amblycephalidæ, or Blunt Heads, are very singularly distributed, being nearly equally divided between Tropical America and the eastern half of the Oriental region, as will be seen by the following statement of the distribution of the genera:—

Amblycephalus (1 sp.), Malay Peninsula to Borneo and the Philippines; Pareas (3 sp.), Assam, China, Java, and Borneo; Asthenodipsas (1 sp.), Malacca; Leptognathus (6 sp.), Central and South America; and Anoplodipsas (1 sp.), supposed to come from New Caledonia, and, if so, furnishing a link, though a very imperfect one, between the disconnected halves of the family.

Family 17.—PYTHONIDÆ. (21 Genera, 46 Species.)

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.)

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)

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.

Acrochordus, inhabits Penang, Singapore, and Borneo; Chersydrus, Southern India and the Malay Peninsula, with a species recently discovered in New Guinea.

Family 20.—ELAPIDÆ. (23 Genera, 100 Species.)

The Elapidæ, or Terrestrial venomous Colubrine Snakes, are an extensive group, spread over the tropics of the whole world, but especially abundant in Australia, where half the known species occur, some of them being the most deadly of venomous serpents. In the Oriental region they are also abundant, containing amongst other forms, the well-known Cobras. The American species are almost equally numerous, but they all belong to one genus, and they are annulated with rings of various colours in a manner quite distinct from any other members of this family. The genera, which are all very distinct, are distributed as follows:—

Diemenia, Acanthophis, Hoplocephalus, Brachiurophis, Tropidechis, Pseudechis, Cacophis, Pseudonaje, Denisonia, and Vermicella, are Australian, the first two ranging to the Moluccas and New Guinea; Ogmodon occurs in the Fiji Islands; Naja, Bungarus, Ophiophagus, Pseudonaje, Xenurelaps, Doliophis, Megærophis, and Callophis are Oriental, one species of the latter genus being found in Japan, while an Ophiophagus has been discovered in New Guinea; Cyrtophis, Elapsoidea, and Pœcilophis are African: Elaps is American, ranging as far north as South Carolina, but not to the West Indian Islands.

Family 21.—DENDRASPIDIDÆ. (1 Genus, 5 Species.)

The single genus Dendraspis, constituting the family, is confined to Tropical Africa.

Family 22.—ATRACTASPIDIDÆ. (1 Genus, 4 Species.)

This small family, consisting of the genus Atractaspis, is also confined to Africa, but has hitherto only been found in the West and South.

Family 23.—HYDROPHIDÆ. (8 Genera, 50 Species.)

The Hydrophidæ, or Sea Snakes, are a group of small-sized marine serpents, abundant in the Indian and Australian seas, and extending as far west as Madagascar, and as far east as Panama. They are very poisonous, and it is probable that many species remain to be discovered. The genera are distributed as follows:—

Hydrophis (37 sp.), ranging from India to Formosa and Australia; Platurus (2 sp.), from the Bay of Bengal to New Guinea and New Zealand; Aipysurus (3 sp.), Java to New Guinea and Australia; Disteira (1 sp.), unknown locality; Acalyptus (1 sp.), South-west Pacific; Enhydrina (1 sp.), Bay of Bengal to New Guinea; Pelamis (1 sp.), Madagascar to New Guinea, New Zealand, and Panama; Emydocephalus (1 sp.), Australian Seas.

Family 24.—CROTALIDÆ. (11 Genera, 40 Species.)

The Crotalidæ, or Pit Vipers, including the deadly Rattlesnakes, form a well-marked family of fanged serpents, whose distribution is very interesting. They abound most in the Oriental region, at least 5 of the genera and 20 species being found within its limits, yet they are quite unknown in the Ethiopian region—a parallel case to that of the Bears and Deer. A few species are peculiar to the eastern portion of the Palæarctic region, while the Nearctic is actually richer than the Neotropical region both in genera and species. This would point to the conclusion, that the group originated in the Indo-Chinese sub-region and spread thence north-east to North America, and so onward to South America, which, having been the last to receive the group, has not had time to develop it largely, notwithstanding its extreme adaptability to Reptilian life. The genera are divided among the several regions as follows:—

Craspedocephalus (7 sp.), Tropical America and the West Indian Islands; Cenchris, Crotalophorus, Uropsophorus, and Crotalus, inhabiting North America from Canada and British Columbia to Texas, one species (Crotalus horridus) extending into South America; Trimeresurus (16 sp.), all India from Ceylon to Assam, Formosa, the Philippines and Celebes; Peltopelor and Hypnale (1 sp. each), peculiar to India; Calloselasma (1 sp.), Siam; Atropos (1 sp.), Java and Borneo; Halys (3 sp.), peculiar to Tartary, Thibet, Japan, North China, and Formosa.

Family 25.—VIPERIDÆ. (3 Genera, 22 Species.)

The Viperidæ, or True Vipers, are especially characteristic of the Palæarctic and Ethiopian regions, only one species being found over a large part of the Oriental region, and another reaching Central India. They are especially abundant in Africa, and the Palæarctic confines in South-western Asia. The common Viper ranges across the whole Palæarctic region from Portugal to Saghalien Island, reaching to 67° North Latitude, in Scandinavia, and to 58° in Central Siberia. The genera, according to Dr. Strauch's synopsis, are distributed as follows:—

Vipera (17 sp.), which has the range of the family, extending over the whole of the Palæarctic and Ethiopian regions, except Madagascar, and as far as Ceylon, Siam, and Java, in the Oriental region; Echis (2 sp.), inhabiting North Africa to Persia and to Continental India; and Atheris (3 sp.), confined to West Africa.

Remarks on the General Distribution of Ophidia.

The Ophidia, being preeminently a Tropical order—rapidly diminishing in numbers as we go north in the Temperate Zone, and wholly ceasing long before we reach the Arctic Circle—we cannot expect the two Northern regions to exhibit any great variety or peculiarity. Yet in their warmer portions they are tolerably rich; for, of the 25 families of snakes, 6 are found in the Nearctic region, 10 in the Palæarctic, 13 in the Australian, 16 in the Neotropical, 17 in the Ethiopian, and no less than 22 in the Oriental, which last is thus seen to be by far the richest of the great regions in the variety of its forms of Ophidian life. The only regions that possess altogether peculiar families of this order, are the Ethiopian (3), and the Oriental (2); the usually rich and peculiar Neotropical region not possessing exclusively, any family of snakes; and what is still more remarkable, the Neotropical and Australian regions together, do not possess a family peculiar to them. Every family inhabiting these two regions is found also in the Oriental; and this fact, taken in connection with the superior richness of the latter region both in families and genera, would indicate that the Ophidia had their origin in the northern hemisphere of the Old World (the ancient Palæarctic region) whence they spread on all sides, in successive waves of migration, to the other regions. The distribution of the genera peculiar to, or highly characteristic of, the several regions is as follows:—

The Nearctic possesses 9; four of these belong to the Colubridæ, one to the Pythonidæ, and four to the Crotalidæ. The Palæarctic region has only 2 peculiar genera, belonging to the Colubridæ and Crotalidæ. The Ethiopian has 25, belonging to 11 families; four to Colubridæ, five to Lycodontidæ, and three to Elapidæ. The Oriental has no less than 50, belonging to 15 families; five are Colubridæ, five Uropeltidæ, twelve Homalopsidæ, six Lycodontidæ, three Amblycephalidæ, eight Elapidæ, and four Crotalidæ. The Australian has 16, belonging to three families only; eleven being Elapidæ, and four Pythonidæ. The Neotropical has about 24, belonging to eight families; ten are Colubridæ, six Pythonidæ, and the rest Dipsadidæ, Scytalidæ, Amblycephalidæ, Elapidæ, and Crotalidæ.

We find then, that in the Ophidia, the regions adopted in this work are remarkably distinct; and that, in the case of the Oriental and Ethiopian, the difference is strongly marked, a very large number of the genera being confined to each region. It is interesting to observe, that in many cases the affinity seems to be rather between the West Coast of Africa and the Oriental region, than between the East Coast and the plains of India; thus the Homalopsidæ—a highly characteristic Oriental family—occur on the West Coast of Africa only; the Dryiophidæ, which range over the whole Oriental region, only occur in Madagascar and West Africa in the Ethiopian; the genus Dipsas is found over all the Oriental region and again in West Africa. A cause for this peculiarity has been suggested in our sketch of the past history of the Ethiopian region, Vol. I. p. 288. In the Lycodontidæ, which are strictly confined to these two regions, the genera are all distinct, and the same is the case with the more widely distributed Elapidæ; and although a few desert forms, such as Echis and the Erycidæ, are common to Africa and the dry plains of India, this is evidently due to favourable climatic conditions, and cannot neutralise the striking differences in the great mass of the family and generic forms which inhabit the two regions. The union of Madagascar with the South-western part of the Oriental region under the appellation Lemuria, finds no support in the distribution of Ophidia; which, however, strikingly accords with the views developed in the Third Part of this work, as to the great importance and high antiquity of the Euro-Asiatic continent, as the chief land-centre from which the higher organisms have spread over the globe.

Fossil Ophidia.—The oldest known remains of Ophidia occur in the Eocene formation in the Isle of Sheppey; others are found in the Miocene (Brown Coal) of Germany, and in some Tertiary beds in the United States. Most of these appear to have been large species belonging to the Pythonidæ, so that we are evidently still very far from knowing anything of the earliest forms of this order. In some of the later Tertiary deposits the poison fangs of venomous species have been found; also a Colubrine snake from the Upper Miocene of the South of France.

Order II.—LACERTILIA.

Family 26.—TROGONOPHIDÆ. (1 Genus, 1 Species.)

The single species of Trogonophis, forming this family, is found only in North Africa.

Family 27.—CHIROTIDÆ. (1 Genus, 1 Species.)

Chirotes, the genus which constitutes this family, inhabits Mexico, and has also been found in Missouri, one of the Southern United States.

Family 28.—AMPHISBÆNIDÆ. (1 Genus, 13 Species.)