Fig. 391.—Larva of Lepidosiren paradoxa 40 days after hatching. (After Kerr.)
Fig. 392.—Larva of Lepidosiren paradoxa 3 months after hatching. (After Kerr.)
In the rainy season when food is abundant the Lepidosiren eats voraciously and stores great quantities of orange-colored fat in the tissues between the muscles. In the dry season it ceases to feed, or, as the Indians put it, it feeds on water. When the water disappears the Lepidosiren burrows down into the mud, closing its gill-openings, but breathing through the mouth. As the mud stiffens it retreats to the lower part of its burrow, where it lies with its tail folded over its face, the body surrounded by a mucous secretion. In its burrow there remains an opening which is closed by a lid of mud. At the end of the dry season this lid is pushed aside, and the animal comes out when the water is deep enough. When the waters rise the presence of Lepidosirens can be found only by a faint quivering movement of the grass in the bottom of the swamp. When taken the body is found to be as slippery as an eel and as muscular. The eggs are laid in underground burrows in the black peat. Their galleries run horizontally and are usually two feet long by eight inches wide. After the eggs are laid the male remains curled up in the nest with them. In the spawning season an elaborate brush is developed in connection with the ventral fins.
Protopterus, a second genus, is found in the rivers of Africa, where three species, P. annectens, P. dolloi, and P. æthiopicus, are now known.
The genus has five gill-clefts, instead of four as in Lepidosiren. It retains its external gills rather longer than the latter, and its limbs are better developed. The habits of Protopterus are essentially like those of Lepidosiren, and the two types have developed along parallel lines doubtless from a common ancestry. No fossil Lepidosirenidæ are known.
Fig. 393.—Protopterus dolloi Boulenger. Congo River. Family Lepidosirenidæ. (After Boulenger.)
Just as the last page of this volume passes through the press, there has appeared a bold and striking memoir on the "Phylogeny of the Teleostomi," by Mr. C. Tate Regan of the British Museum of Natural History. In this paper Mr. Regan takes the view that the Chondrostean Ganoids (Palæoniscum, Chondrosteus, Polyodon, Psephurus, etc.) are the most primitive of the Teleostomous fishes; that the Crossopterygii, the Dipneusti, the Placodermi, and the Teleostei (as well as the higher vertebrates) are descended from these; that the Coccosteidæ (Arthrodires) are the most generalized of the Placoderms, the Osteostraci and most of the other forms called Ostracophores (Antiarcha, Anaspida) being allied to the Arthrodires, and to be included with them among the Placodermi; that the cephalic appendage of Pterichthyodes, etc., is really a pectoral fin; that the Heterostraci (Lanarkia, Pteraspis, etc.) are not Ostracophores or Placoderms at all, but mailed primitive sharks, derived from the early sharks as the Chimæras are, and that the Holostean Ganoids (Lepisosteus, Amia, etc.) should be separated from the Chondrostei and referred to the Teleostei, of which they are the primitive representatives.