[50] Swordfish or sturgeon (L. and S. Lexicon), or Centriscus scolopax. [51] A variegated fish. [52] Perca fluviatilis. [53] Silurus glanis. [54] Cyprinus carpis, Carp. [55] Xiphias gladius, Swordfish. 5. And fish differ in other respects besides their gills, for they have no hair like viviparous quadrupeds, nor scaly plates like oviparous quadrupeds, nor feathers like birds, but the greater number of them are covered with scales; some of them are rough, and a very few are smooth. Some cartilaginous fishes are rough, others smooth. Congers, eels, and tunnies are smooth. All fish except the scarus have pointed teeth, and all have sharp teeth, some several rows of them, and teeth on the tongue; they have also a hard prickly tongue, so united to the mouth as sometimes to appear without a tongue. 6. The mouth of some fishes is wide, like viviparous quadrupeds. They have no external organs of sense, nor even passages for smelling or hearing; but all have eyes without eyelids, though their eyes are not hard. All fishes are sanguineous; some are oviparous, others viviparous; all those that are covered with scales are oviparous. The cartilaginous fishes are all viviparous, except the batrachus. CHAPTER X. 1. The remaining class of sanguineous animals is that of serpents; these partake of both characters. The greater portion of them inhabit the land, a few inhabiting water are found in rivers. There are also serpents in the sea very like those on land, except in their head, which is more like that of the conger. There are many genera of sea-serpents, and they are of all kinds of colours; they do not exist in the deepest part of the ocean. Serpents are apodal, like fishes. 2. There are also marine scolopendræ,[56] very like those on land, but rather less; they live in rocky places; in colour they are redder, and they have more feet, and slighter legs than in the terrestrial species. These also, like the serpents, are not found in deep places. [56] Nereis, or aphrodite. 3. And there is a small fish which lives among the rocks, which some call echineis;[57] some people use it for trials and philtres; it is not fit for food. Some people say it has feet, but it has none; the fins, however, are like feet, which gives it this appearance. I have now described the external parts of sanguineous animals, their nature, and their number, and the differences which occur amongst them. [57] Echeneis remora. CHAPTER XI. 1. First of all we will speak of the internal parts of sanguineous animals, for the greatest number of genera differ from other animals, some being sanguineous, others ex-sanguineous. The sanguineous genera are man, viviparous and oviparous quadrupeds, birds, fishes, and whales, and perhaps others that are anonymous, because they do not form a genus, but simply species amongst each other, as the serpent and the crocodile.