Fig. 234.—Ophiocephalus striatus, India.
Sixteenth Division—Acanthopterygii Labyrinthibranchii.
Body compressed, oblong or elevated, with scales of moderate size. A superbranchial organ in a cavity accessory to that of the gills.
First Family—Labyrinthici.
Dorsal and anal spines present, but in variable numbers; ventrals thoracic. Lateral line absent, or more or less distinctly interrupted. Gill-opening rather narrow, the gill-membranes of both sides coalescent below the isthmus, and scaly; gills four; pseudobranchiæ rudimentary or absent.
Fig. 235.—Superbranchial organ of Anabas.
Freshwater-fishes of the Cyprinoid division of the Equatorial zone. They possess the faculty of being able to live for some time out of the water, or in thick or hardened mud, in a still greater degree than the fishes of the preceding family. In the accessory branchial cavity there is lodged a laminated organ which evidently has the function of assisting in the oxygenisation of the blood. In Anabas it is formed by several exceedingly thin bony laminæ, similar in form to the auricle, and concentrically situated one above the other, the innermost being the largest. The degree in which these laminæ are developed is dependent on age. In specimens from one inch and a half to two inches and a half long there are only two such laminæ, a third being indicated by a small protuberance at the central base of the second or outer laminæ. In specimens of from three to four inches in length the third lamina is developed, covering one-half of the second. The edges of all the laminæ are straight, not valanced. In specimens of from four to five inches a fourth lamina makes its appearance in the basal centre of the third lamina. The other laminæ continue to grow in their circumference, and their edges now become undulated and slightly frilled. Cuvier and Valenciennes have examined still larger specimens. The figure given by them and reproduced here was taken from a specimen six or seven inches long, and shows the superbranchial organ composed of six laminæ.
The air-bladder of the majority of these fishes is very large, extending far into the tail, and, therefore, divided behind by the hæmal spines into two lateral portions.
The Labyrinthici are generally of small size; they are capable of being domesticated, and some of them deserve particular attention on account of the dazzling beauty of their colours or the flavour of their flesh.