have received from naturalists the expressive name of Dipnoi, a term formed from two Greek words, meaning animals with twofold respiration.
Two genera, each comprising only one species, make up this subclass Dipnoi. Gambia, Zanzibar, Senegal, the region of the White Nile, and the Niger, are the native haunts of the African species, the Protopterus annectens, or anguilliformis; the other species, Lepidosiren paradoxa, is found in the valley of the Amazonas.
The latter species is but ill represented in collections; there are in Europe only a very few specimens. According to Mr. Bates, the natives call it zambaki mboya; this naturalist says that the Lepidosiren has even penetrated to the great lakes in the vicinity of the Tapajos and the Madeira. M. de Castelnau has caught this animal in a marsh on the left bank of the Amazonas, above Villanova, at a place called Caracauca.
In Lepidosiren the tail is pointed; the pectoral and ventral fins, which stand far apart, are not long, and consist of a single ray, not divided into segments. The general form is that of an eel, with two threads hanging on each side. In color the animal is dark brown-gray, or olive, with round spots of lighter color, about the size of the scales, and indistinct on the head and the middle of the back. The species appears to grow to the length of about one metre.
The protopterus, or African representative of the group, is olive-green in color, this tint being varied with-a number of irregular brown or blackish spots. The lower portions are violet. The young are marked with fine lines of light color, which cross each other, forming a regular network. The extremity of the tail is tapering. The pectoral and ventral fins are long, and consist of one ray made up of jointed segments. The bones of the skeleton are of a green hue.
For our first acquaintance with these animals we are indebted to the naturalist Natterer, who, during his visit to Brazil, obtained two specimens, which he placed in the Vienna Museum. For a long time the Protopterus and Lepidosiren were classed with those batrachians in which the tail persists, as in the axolotl. Later they were considered as forming a sort of intermediate class between reptiles and fishes, and as forming the connecting link between the two. At present naturalists class Lepidosiren and Protopterus among fishes.
The Dipnoi are not the only class of animals that bury themselves in the dried-up mud after the water has been evaporated by the heat of summer. There is another fish that does the same the—mud-fish (Amia), which is found in the fresh waters of the United States. The Amia, too, is indisputably a fish. There appears to exist some relation between this animal's mode of life and the cellular structure of its air-bladder. Still, the Amia is not an amphibian, in the strict sense of the term. For, though its air-bladder resembles the lung of
