The first great group of Cartilaginous Fishes is divided into three sections, which make in reality four families, as the second section comprises two. In the first of these we find the queer family of Lampreys, in which the mouth forms a sucker. In the second, are the family of Raias, and the Shark family, characterized by their mouth being furnished with jaws. The third includes the Sturgeons, which are distinguished by having the gills free. The Bony Fishes are divided into four great sections. The first is represented by the family of Globe Fish and Coffers, which have the jaw attached to the cranium. The second includes the queer family of Pipe-fish and Sea-horses, which have the gills divided into round tufts arranged in pairs. The third division includes the family of soft-finned Fishes, in which the rays of the fins are soft. In the fourth section are the various families of spiny-finned Fishes. And in some one of these groups with their distinct characteristics, may be classified all the numerous Fishes that are known to modern Naturalists. CARTILAGINOUS FISHES. THE LAMPREYS AND THE EELS. It is not usual to class these two families together, but they look so much alike until studied closely, all the different varieties having the appearance of serpents, with fins and curious forms of tails and heads, that it seems best to study them together and find the points of difference. The Lamprey is of a lighter color than the Eel, and is not so graceful, but of a rather clumsy form. But it differs most in its mouth, which is round, and placed below the end of the nose. It resembles the mouth of a Leech more than that of an Eel. The Lamprey has a hole on top of its head through which it spouts water, somewhat like a Whale, and the fins are formed by a lengthening out of the skin instead of having a set of bones or spines for that purpose. The mouth of the Lamprey is not only formed like that of the Leech, but it has the same property of sticking close to and sucking any body that is applied to it. It has a wonderful power of holding on to stones by sucking with its mouth, so that it is almost impossible to draw it away. We are told of one that weighed only three pounds, and yet it stuck so firmly to a stone weighing twelve pounds, that it remained suspended by its mouth, and it was almost impossible to make it loosen its hold. This wonderful strength of suction is supposed to arise from the power of the Lamprey to exhaust the air within its body by the hole over the nose, while the mouth is closely fixed to the object, and allows no air to enter. This adhesive or sticking quality in the Lamprey is somewhat increased by the slimy substance which is smeared all over its body. This substance serves to keep it warm in the cold water, and it also keeps its skin soft and pliant.