The TRILOBITE was an animal which appears at one time to have been spread over the whole earth, or in the waters on the earth. There were a great variety of these animals. They derive their name from their peculiar form, appearing like three lobes. They were covered with a shell called a shield. This creature is supposed to be the first articulated animal found among the ancient animals of the earth, which perished probably about the time of the subsidence of the coal formation. The legs of this creature were made to be employed to perform the double purpose of paddles and lungs. Geologists have been fortunate in discovering, after so long a time, the curious visual organ of this extinct race. We have referred to the eye of this creature, which operates by facets or lenses. There appear two elevated cones in the head of the animal, three parts of which are full of eyes, called compound eyes. They see objects in the axis of the cones, the field of vision being larger or smaller as the exterior of the eye is more or less hemispherical. The eye of the trilobite is nearly the frustum of a cone, incomplete on one side, opposite to each other, where they would have been unnecessary. Samples of petrifactions of this animal may be found in any of the geological collections. The CEPHALOPOD was a shelled animal, highly and strongly organized. It is so called because the organs of motion are arranged around the head. It appears destitute of armor, but probably was one of the most powerful of its race, attacking, seizing, and devouring great numbers of creatures which it killed. The arms or feet which were around the head brought the victim immediately to the mouth of this formidable animal. The office of these creatures seems to have been to restrain the excessive increase of creatures of the transition and secondary periods. There are many varieties of these animals, as the nautili, amonites, and pompilus. There are many others, as the orthus, the penamerus, and the orthoceratites. THE BELEMNITE.-This was a shelled animal, of conical form, with a cavity of a like shape, |