Fig. 118.—Chilomycterus tigrinus (Indian Ocean). (After Savtschenko.)
C.—Teleostei.—Physostomi.
This Order is characterised by the presence of a pneumatic duct to the air-bladder. It consists of a large, number of families, only two of which, the Siluridæ and Murænidæ, include venomous species.
1.—Siluridæ.
The majority of the very large number of species belonging to this family live in fresh water, and have the free margin of the lips almost always furnished with barbules (Silurus glanis; [fig. 119]). A few of them possess a poison-apparatus, which, however, attains its greatest development in Plotosus, the only genus of Siluridæ found exclusively in the sea.
The species of Plotosus frequent the shores of the Indian Ocean, and are met with in the Seychelles, Réunion, and Mauritius. In shape they resemble eels, and they bury themselves in the sand or mud, a habit which renders them very dangerous to fishermen.
Fig. 119.—Silurus glanis (Rivers of Central and Eastern Europe).
Plotosus lineatus, which is of a greenish-brown colour, striped with from four to six longitudinal whitish bands, is the most common. By the Creoles of Mauritius and Réunion it is called Machoiran, by the Malays Sambilang, and by the Abyssinians Koomat.
Its poison-apparatus is situated at the base of the dorsal and pectoral spines. These spines are strong, sharp, slightly incurved, and furnished with hooked denticulations, which cause them to remain in the wound, in which they break off. Near their extremity there opens a small canal, which communicates with the culs-de-sac situated at the base of the spiny rays, which produce a venomous secretion. The dorsal spine has only a single cul-de-sac, while the pectoral spines have two.