Fig. 262.—Euglyptosternum coum, thoracic adhesive apparatus.
Euglyptosternum.—Adipose fin of moderate length; a short dorsal with a pungent spine and six rays; anal fin short. Barbels eight, of which one pair is placed between the anterior and posterior nostrils which are close together. Teeth on the palate villiform, in two separate patches. Eyes small, below the skin. Caudal forked; ventral rays six. Pectorals horizontal, with a thoracic adhesive apparatus between, which is formed by longitudinal plaits of the skin.
This fish (Eu. coum) inhabits the river Coic in Syria, and is about twelve inches long. The plaited structure on the thorax probably increases the capability of the fish of maintaining its position in the rapid current of the stream, a function which appears to be chiefly performed by the horizontally expanded pectoral fins. A similar structure is found in Glyptosternum, a genus represented by eight species in mountain streams of the East Indies, and differing from the Syrian species in lacking the teeth on the palate.
V. Siluridæ Stenobranchiæ.—The rayed dorsal fin is short, if present, belonging to the abdominal portion of the vertebral column, the ventrals being inserted behind it (except in Rhinoglanis). The gill-membranes are confluent with the skin of the isthmus.
a. Doradina.
Some of the genera have no bony shields along the lateral line, and a small adipose fin or none whatever; all of these are South American—Ageniosus, Tetranematichthys, Euanemus, Auchenipterus, Glanidium, Centromochlus, Trachelyopterus, Cetopsis, and Astrophysus.
Others have a series of bony scutes along the middle of the side; they form the genus Doras with two closely allied forms, Oxydoras and Rhinodoras. Some twenty-five species are known, all from rivers of tropical America, flowing into the Atlantic. These fishes have excited attention by their habit of travelling, during the dry season, from a piece of water about to dry up, in quest of a pond of greater capacity. These journeys are occasionally of such a length that the fish spends whole nights on the way, and the bands of scaly travellers are sometimes so large that the Indians who happen to meet them, fill many baskets of the prey thus placed in their hands. The Indians supposed that the fish carry a supply of water with them, but they have no special organs, and can only do so by closing the gill-openings, or by retaining a little water between the plates of their bodies, as Hancock supposes. The same naturalist adds that they make regular nests, in which they cover up their eggs with care and defend them, male and female uniting in this parental duty until the eggs are hatched. The nest is constructed at the beginning of the rainy season, of leaves, and is sometimes placed in a hole scooped out in the beach.
Finally, in the last genus, the lateral scutes are likewise absent, viz. in
Synodontis.—The adipose fin is of moderate length or rather long; the dorsal fin has a very strong spine and seven soft rays. The teeth in the lower jaw are movable, long, very thin at the base, and with a slightly-dilated brown apex. Mouth small. Barbels six, more or less fringed with a membrane or with filaments. Neck with broad dermal bones.