As to the various species which were used for different purposes, we know really nothing, the Jews merely dividing their Fish into clean and unclean. Some of the species to which the prohibition would extend are evident enough. There are, for example, the Sheat-fishes, which have the body naked, and which are therefore taken out of the list of permitted Fishes. The Sheat-fishes inhabit rivers in many parts of the world, and often grow to a very considerable size. They may be at once recognised by their peculiar shape, and by the long, fleshy tentacles that hang from the mouth. The object of these tentacles is rather dubious, but as the fish have been seen to direct them at will to various objects, it is likely that they may answer as organs of touch. [Illustration: 1. MURÆNA. 2. LONG-HEADED BARBEL. 3. SHEAT-FISH.] As might be conjectured from its general appearance, it is one of the Fishes that love muddy banks, in which it is fond of burrowing so deeply that, although the river may swarm with Sheat-fishes, a practised eye is required to see them. As far as the Sheat-fishes are concerned, there is little need for the prohibition, inasmuch as the flesh is not at all agreeable in flavour, and is difficult of digestion, being very fat and gelatinous. The swimming-bladder of the Sheat-fish is used in some countries for making a kind of isinglass, similar in character to that of the sturgeon, but of coarser quality. The lowermost figure in the above illustration represents a species which is exceedingly plentiful in the Sea of Galilee. On account of the mode in which their body is covered, the whole of the sharks and rays are excluded from the list of permitted Fish, as, although they have fins, they have no scales, their place being taken by shields varying greatly in size. The same rule excludes the whole of the lamprey tribe, although the excellence of their flesh is well known. Moreover, the Jews almost universally declare that the Muræna and Eel tribe are also unclean, because, although it has been proved that these Fishes really possess scales as well as fins, and are therefore legally permissible, the scales are hidden under a slimy covering, and are so minute as to be practically absent. The uppermost figure in the illustration represents the celebrated Muræna, one of the fishes of the Mediterranean, in which sea it is tolerably plentiful. In the days of the old Roman empire, the Muræna was very highly valued for the table. The wealthier citizens built ponds in which the Murænæ were kept alive until they were wanted. This Fish sometimes reaches four feet in length. The rest of the Fishes which are shown in the three illustrations belong to the class of clean Fish, and were permitted as food. The figure of the Fish between the Muræna and Sheat-fish is the Long-headed Barbel, so called from its curious form.