By one or other of these various methods the air-bladder is either known to be sound-producing, or is believed with good reason to be such, in the following Teleosts,[424] and many others:—Certain species of the South-American genera of Siluridae, _Pimelodus_, _Sorubim_, _Platystoma_, _Piratinga_, _Centromochlus_, and _Trachelyopterus_; species of the South-American family Characinidae; _Amblyopsis spelaea_, the blind Fish from the Mammoth Cave of Kentucky (Amblyopsidae); among the Syngnathidae, the short-snouted Sea-Horse (_Hippocampus brevirostris_) of the British Coasts; certain Sclerodermi, such as the Trigger-Fishes, _Batistes vetula_, _Triacanthus brevirostris_, _T. biaculeatus_, and _Monacanthus pardalis_, and also some "Coffer Fishes" (_e.g._ species of _Ostracion_); some Gymnodontes (species of _Diodon_ and _Tetrodon_); a few Serranidae (_e.g._ species of _Therapon_ and _Pristipoma_); species of _Holacanthus_ (Chaetodontidae) and in _Holocentrum sogho_ (Berycidae); such Sciaenidae as the "Drum" (_Pogonias chromis_), the "Maigre" (_Sciaena aquila_), which has sometimes been taken in British waters, _Umbrina cirrhosa_, _Otolithus regalis_, and _Micropogon undulatus_, and, with more or less probability, many other species of the same family; one species of Zeidae, the John Dory (_Zeus faber_); _Batrachus tau_ among the Batrachidae; several species of Gurnards (Triglidae) belonging to the genera _Prionotus_ and _Trigla_; the so-called Flying Gurnard, _Dactylopterus volitans_ (Dactylopteridae); the Indian species _Ophiocephalus marulius_ and _O. gachua_ (Ophiocephalidae); amongst the Gadidae, the Cod (_Gadus morrhua_) and the Haddock (_G. aeglefinus_); in such Zoarcidae as the blind Fish (_Lucifuga subterranea_) from the subterranean waters of the caves of Cuba, and also in some Ophidiidae (_e.g._ species of _Ophidium_). In Fishes other than Teleosts, instances of normal sound-production by special vocal structures are rare. No recorded instances are known in the Cyclostomes or the Elasmobranchs,[425] {362}but there is evidence that sounds are emitted by _Polypterus_ among the Crossopterygii, and by the Dipnoids _Neoceratodus_,[426] _Protopterus_, and _Lepidosiren_, although it is not certainly known how they are produced, or that they may not be the accidental concomitants of the inspiratory or expiratory action of the lungs in breathing. As to the nature of the sounds produced by the air-bladder and its muscles in different Teleosts, a few examples may be given.