Synodontis is characteristic of the fauna of tropical Africa, where it is represented by fifteen species. Several occur in the Nile, and are known by the vernacular name “Schal.” Some attain a length of two feet. The species figured is from West Africa, and characterised by its long upper jaw.
Fig. 263.—Synodontis xiphias.
b. Rhinoglanina.
Rhinoglanis.—Two dorsal fins, both composed of rays, the first with a strong spine; anal rather short. Barbels six; anterior and posterior nostrils close together, the posterior very large, open. Neck with broad dermal bones. Ventrals with seven rays, inserted below the posterior rays of the first dorsal fin.
This Siluroid is known from a single example only one and a half inches long, obtained at Gondokoro on the Upper Nile. Callomystax represents this type in the Ganges and Indus.
c. Malapterurina.
Malapterurus.—One dorsal fin only, which is adipose and situated before the caudal; anal of moderate length or short; caudal rounded; ventrals six-rayed, inserted somewhat behind the middle of the body; pectorals without pungent spine. Barbels six: one to each maxillary and two on each side of the mandible. The anterior and posterior nostrils are remote from each other. No teeth on the palate. The entire head and body covered with soft skin. Eyes small. Gill-opening very narrow, reduced to a slit before the pectoral.
The “Electric Cat- or Sheath-fishes” are not uncommon in the fresh waters of tropical Africa; three species have been described, of which M. electricus occurs in the Nile; they grow to a length of about four feet. Although the first dorsal fin is absent, its position (if it had been developed) is indicated by a rudimentary interneural spine, which rests in the cleft of the neural process of the first vertebra. The electric organ extends over the whole body, but is thickest on the abdomen; it lies between two aponeurotic membranes, below the skin, and consists of rhomboidal cells which contain a rather firm gelatinous substance. The electric nerve takes its origin from the spinal chord, does not enter into connection with ganglia, and consists of a single enormously-strong primitive fibre, which distributes its branches in the electric organ.
