Of the _Colubrinæ_, _Rhinechis scalaris_, _Coluber æsculapii_, _C. quadrilineatus_, _Elaphis quater-radiatus_, and three species of _Zamenis_ inhabit Europe: there are five of _Coluber_ in North America, and the well-known "Black Snake" of the Anglo-Americans is the _Coryphodon constrictor_. Other species of _Coryphodon_ or _Ptyas_ inhabit South-eastern Asia, as the different "Rat Snakes" of Anglo-Indians, of which _Ptyas mucosus_ is particularly common in India, where it is encouraged by reasonable people as a destroyer of the far more troublesome Brown Rat (_Mus decumanus_). The _Dryadinæ_ are chiefly American, and do not call for particular further remark; but the _Natricinæ_ are very numerous, and there are three species in Europe of its most prominent genus, _Tropidonotus_--viz. _T. natrix_, _T. hydrus_, and _T. viperinus_. [Dr. Günther gives as many as twenty-one species of this genus as inhabitants of the Indian region alone, and there is reason to believe that that number is far from being complete. Others inhabit North America and North-western Australia, and some generic groups have been detached that are not very conspicuously separable.] [Illustration: Fig. 11.--Ringed Snake (_Tropidonotus natrix_).] The Ringed Snake, _Tropidonotus natrix_, is often found in fine seasons near human habitations. It deposits its eggs, which are fifteen to twenty in number, commonly in dunghills, in one agglutinated mass. Exposed to the air, these eggs soon shrivel and dry, and the embryos within them perish. The Ringed Snakes are also found near rivers and meadows, by the side of water-courses, into which they love to plunge; hence they are sometimes called Water Serpents, Swimming Serpents, Hedge Eels, and other provincial synonyms. They sometimes attain to as much as and more than a yard in length. The summit of their head is covered with nine large scales, disposed in four rings. The upper part of the body is of a more or less darkish grey colour, marked on each side with irregular black spots. Between the two rows of spots are two other longitudinal rows, which extend from the head to the tail. The belly varies from black to a bluish white. Upon the neck are two whitish or pale yellowish spots, which form a kind of half collar or ring, from which its name is derived; these two spots become much more apparent from being contrasted with two other very dark triangular spots placed near them. They prey upon lizards, frogs, and mice, and they even surprise young birds, and devour the eggs in their nests, for they climb trees with facility. Towards the end of the autumn they seek the warmest places, approaching near to houses; or they retire into subterranean holes, often at the bottom of some hedge, which is almost always in an elevated place, secure from inundations. The Ringed Snake is found in nearly all European countries, and can be handled without danger. Lacépède gives some interesting details, showing the gentleness of its habits.