The _Colubridæ_ are divided by Dr. Günther into ground Colubrines (_Coronellinæ_), true Colubrines (_Colubrinæ_), bush Colubrines (_Dryadinæ_), and fresh-water Colubrines (_Natricinæ_); and he remarks that "they are found in every part of the temperate and tropical regions, but are only scantily represented in Australia and in the islands of the Pacific. The species are so numerous and show such a gradual passage between extreme forms, that, although genera can be easily characterized, it is almost impossible to distinguish wider groups by definite characters." Among them the _Coronellinæ_ approximate the immediately preceding families, and, like them, live on the ground, and are not generally of brilliant colouring, though a few species which frequent grassy plains are of a bright green colour. The _Colubrinæ_ "form, as it were," writes Dr. Günther, "the nucleus of the whole sub-order of innocuous Snakes: they are typical forms, not characterized by the excessive development of some particular organ, but by the fairness of the proportions of all parts. Yet some of them have a more slender body than others which always live on the ground; they are land Snakes, but swim well when driven into the water, or climb when in search of food. They are of moderate or rather large size." In the _Dryadinæ_ the form is elongate and somewhat compressed, indicating their climbing propensities; they have the body not so excessively slender as in the true Tree Snakes, to which they lead off. They are much more numerous in the New World than in the Old, and their ground-colour is very commonly green. The _Natricinæ_ are generally not very elongate or compressed, and most of them have keeled scales. They freely enter the water in pursuit of their food, which consists chiefly of frogs and fishes. All the Snakes of the preceding three sub-families overpower their prey by throwing some coils of the body round or over it, and commence to swallow it only after it has been smothered, or at least exhausted; but the _Natricinæ_ swallow their prey immediately after they have seized it. Of the sub-family _Coronellinæ_, one species of the typical genus _Coronella_ is widely diffused over Europe, and has only of late years been recognised as an inhabitant of the British Islands, the _Coronella austriaca_. Another, _C. girondica_, occurs in Italy. Others are found in Africa, America, and Australia. The _C. austriaca_ has somewhat the appearance of the common Adder, for which it is often mistaken; but it is non-Venemous, though rather a fierce reptile, which bites and holds on; and as it occurs in Malta (where no Venemous species is known to exist), it is doubtless the supposed Viper which seized upon the apostle Paul. Several other genera are recognised.