[Illustration: FIG. 116.--_Tetrodon rubripes_ (Japan). (After Savtschenko.)] Closely allied to _Diodon_, and feared like the foregoing on account of their spines, which are sometimes scattered all over the body, are the species of the genus _Chilomycterus_, the most important of which are _C. orbicularis_ (fig. 117), and _C. tigrinus_ (fig. 118), both of which are found in the Indian Ocean. [Illustration: FIG. 117.--_Chilomycterus orbicularis_ (Indian Ocean). (After Savtschenko.)] [Illustration: 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. [Illustration: 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. The contraction of the local muscles, by compressing these culs-de-sac, can cause the venom to make its way into the canal of the spine, but the fluid does not spurt forth in a jet as in the case of _Synanceia_. The poison-apparatus is therefore passively defensive in character. _Plotosus_ is capable of wounding only when the hand or foot is placed on its dorsal or pectoral spines. Fishermen who are stung immediately feel an excruciating pain, which is soon accompanied by fever, and lasts for several days. Accidents caused by this fish are of fairly common occurrence in Réunion. 2.--Murænidæ.