XIII SOUND-PRODUCING ORGANS 361 
undoubtedly constitute a vocal organ, there are many others 
in which the bladder can only be inferred to be sound-producing 
from its general agreement in anatomical structure with the 
same organ in Fishes where its vocal function has been clearly 
proved. 
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,' 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 Chara- 
cinidae ; 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, 
Balistes 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 (eg. species of Zherapon and 
Pristipoma) ; species of Holacanthus (Chaetodontidae) and in 
Ffolocentrum sogho (Berycidae) ; such Sciaenidae as the “ Drum ” 
(Pogomas 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 (Ophio- 
cephalidae); 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,” 
1 Sorensen, Lydorganer, p. 82, et. seq. 
2 Cf. Mettenheimer, Arch. f. Anat. u. Physiol. 1858, p. 302. 
