Thus the crocodiles of the Nile and the Ganges, the Gavials with their long narrow snouts, and the Alligators of America, with their shorter and broader heads, feed on fish and beasts, and all dead and putrid matter, acting as scavengers of the rivers; while they themselves are almost free from attack, except when tigers fall upon them on land. But it is the young crocodiles which run the most risks when they come out of the small chalky eggs which have been hatched in the warm sand of the shore. True, their mother often watches over them at this time, and even feeds them from her own mouth; but in spite of her care many of them are eaten in their youth by the tortoises and fishes which they would themselves have devoured by-and-by, if they had lived to grow up; while the monitors, ichneumons, waterfowl, and even monkeys, devour large numbers of crocodiles’ eggs. * * * * * And now, if we were to turn our backs upon the great rivers in which these animals dwell, and wander into the Indian jungle or the South American forest, we might meet with enemies far more dangerous and deadly, although they stand much lower in the reptile world. Who would think that the huge boa of South America, and the python and poisonous cobra of India, or even our own little viper, whose bite is often death to its victim, are creatures of lower structure than the harmless little lizard or the stupid alligator? Yet so it is. For Snakes have no breastbone and have lost all vestiges of front legs and shoulder bones, nor have they any hips or hind legs except among the boas and rock-snakes; and even these have only small traces of hips, which carry some crooked bones, ending in horny or fleshy claws, in the place where hind legs ought to be. They have no eyelids (and by this we may know them from the legless lizards), but their skin grows right over the eyes, so that when a snake casts its skin there are no holes where the eyes have been, but only clear round spaces like watch-glasses, in the scaly skin. Their ears have no drum, and are quite hidden under the scales with which their body is so thickly covered that they must feel very little as they glide along. These scales, like those of the lizard, are thickened parts of the outer skin, and if you stretch a piece of snake-skin you can see them lying embedded in it, the clear skin itself showing between. [Illustration: Fig. 26. Skeleton of a Snake. _sp_, Spinous processes of the joints; _r_, ribs; _q_, quadrate bones, joining upper and lower jaws; _e_, front of the lower jaw, where there is an elastic band in the place of bone; _b_, ball end of joint, facing the tail; _c_, cup end of joint, facing the head. ]