Читать книгу Peter Parley's Wonders of the Earth, Sea, and Sky онлайн

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If you have ever seen a crocodile open its mouth, and then snap together its long thin jaws, so as to make you start with the noise, you will see how necessary all these contrivances must be for him and the Icthyosaurus, whose jaws were still thinner, to prevent them from breaking their bones.

This however is not at all more wonderful than the eye, which in the old-fashioned animal I have been describing, was much larger than that of the crocodile, and not unfrequently bigger than a man's head. From the very great quantity of light which such a large surface would receive, the creature's power of seeing must have been very great. And besides this advantage, it had the same faculty as is possessed by the golden eagle, the turtle, the tortoise, and the lizard, of pressing the eye forward to render it more convex. In man and most animals, the eye is placed in a fixed cavity of thin bone, something like an egg-cup, but in the Icthyosaurus, the cavity was formed by several bones not quite touching each other; (as you may see in the last cut, and in figure 2, you have two of the bones by themselves, taken out of the socket of the eye;) and there were muscles to draw these bones closer together; so that by making the cup less deep, the eye was thrust forward and made to swell out in the middle. This is illustrated in the ball b, which is pressed outwards, by drawing the plates of bone cc, together at o, close than those which have the ball a between them.