(_c_) A characteristic feature in the air-bladder of many Teleosts belonging to widely different families is the development of a more or less complex system of simple, or variously branched, caecal outgrowths, which, like the internal septa, are specially characteristic of those Fishes in which the bladder is used as a vocal organ without, however, being peculiar to them. In some of the Gadidae, as in the Cod (_Gadus morrhua_), the air-bladder divides anteriorly into a pair of caecal prolongations which extend forwards to the head, and are often curiously coiled. Somewhat similar caeca are also present in species of Berycidae, Sparidae, Siluridae, Clupeidae, and Notopteridae. Caecal prolongations may also be developed from the hinder end of the bladder, and, as already mentioned, extend into the tail; or even from both ends in the same species (e.g. _Notopterus_).[340] In the Silurid, _Rita crucigera_,[341] a long tubular caecum is developed from each side of the heart-shaped bladder, and thence is prolonged backwards to the anus. In certain species of _Doras_ of the same family (e.g. _D. maculatus_),[342] an elegant series of variously sized branched caeca fringe each of the lateral margins of the bladder. It is, however, in the Physoclist family of the Sciaenidae[343] that the branching of the air-bladder attains its greatest development in extent and variety. {304}[Illustration: FIG. 180.—Air-bladder of _Otolithus_. (From Cuvier and Valenciennes.)] In _Otolithus_ (Fig. 180) two short tubular canals are given off from the antero-lateral angles of the bladder, each subsequently dividing into two elongated, tapering sacs, of which one is directed forwards and the other backwards. In _Corvina lobata_ (Fig. 181) the lateral margins of the bladder are everywhere fringed with a series of tufts of caeca, each tuft being connected by a short common canal with the cavity of the organ. In the "Drum" (_Pogonias chromis_) (Fig. 182) each side of the anterior third of the air-bladder has a series of digitately branched caecal appendages, the most posterior of which on each side are connected by a tubular canal, also bearing branched caeca, with the corresponding postero-lateral extremity of the bladder.