Lives of Eminent Zoologists, from Aristotle to Linnæus / with Introductory remarks on the Study of Natural History

by William MacGillivray

IV. Nantes, Swimming Amphibia. Respiring at will by means of gills and lungs: the rays of the fins cartilaginous.

These animals, of which 76 species are enumerated, are referred to fourteen genera,—the lamprey, ray or skate, shark, chimæra, frog-fish, sturgeon, lump-fish, oldwife-fish, bonyskin-fish, sun-fish, porcupine-fish, trumpet-fish, pipe-fish, and dragon-fish.

The number of species described as belonging to this class is 292. The specific characters are derived from various circumstances connected with the external conformation; in the tortoises, from the shell and feet; in the snakes, from the number of the abdominal and caudal plates; in the swimming amphibia, or, as they are now more properly called, the cartilaginous fishes, from the form of the body, the differences of the fins, and other circumstances.

The fourth class, that of Fishes, contains four orders, founded upon the relative position of the fins, which are compared to the feet of other animals. Thus, the ventral fins may be placed before, beneath, or behind the pectoral, or they may be wanting.

I. Apodes, Apodal or Footless. Fishes destitute of ventral fins; such as the eel, the wolf-fish, and the sword-fish.

II. Jugulares, Jugular. Fishes having the ventral fins placed before the pectoral; as the dragonet, weever, cod, haddock, and coal-fish.

III. Thoracici, Thoracic. Fishes having the ventral fins placed under the pectoral; as the goby, bull-head, holibut, gilt-head, perch, mackerel, &c.

IV. Abdominales, Abdominal. Fishes having the ventral fins placed on the abdomen behind the pectoral fins; as in the salmon, trout, pike, mullet, and herring.

In this class there are 47 genera, and 400 species. The specific characters are taken from the number of rays in the fins, the form of the tail, the cirri or filaments at the mouth, the colouring of the body, the form of the scales, and other circumstances.

The fifth class, that in which the Insects are included, comprehends 86 genera, disposed into seven orders, which are founded on the number and texture of the wings.