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THE ICHTHYOSAURUS.

That large animal lying on the ground, is called the Icthyosaurus, from two Greek words signifying Fish-Lizard, in consequence of his possessing some of the peculiarities of both fishes and lizards.

The usual length of this creature was from twenty to thirty feet. It possessed a most surprising combination of the powers and qualities of different animals which are now in existence. In its general form and character it must have been something like the modern porpoise; but it had the teeth of a crocodile, the head of a lizard, the back-bone of a fish, and the fins or paddles, of a whale.

I shall spend some little time in explaining to you each of these particulars, that you may see how wisely all the parts of living things are framed to supply their wants, and adapt them to the circumstances in which they are placed.

The head was not very different from that of a crocodile, or lizard, in its general shape. The teeth were precisely like those of a crocodile, and grew up in the same manner. Creatures of this sort lead a ruffian sort of life, always biting something or other, and as they live very much in the dark at the bottom of the water, perhaps now and then snap at a stone or a piece of hard wood by mistake, and often break their teeth; and in order therefore to keep them in constant repair, they have a fresh set once a year, or at very short intervals, so that they are always growing. The young tooth a, springs up inside the old one b, till it becomes so large that it splits its predecessor, and the pieces fall off, just as the covering of some sorts of buds falls off as the flower expands, as you will see in this cut, representing one of the fossil teeth.