508 FISHES CHAP. 



degeneration. Hyo-branchial cleft open, and associated with a 

 pseudobranch. The first four branchial arches carry holobranchs. 

 Air-bladder single. Young not provided with cutaneous gills. 

 Two genera only are known, the Mesozoic Ceratodus and the still 

 living Neoceratodus. The former genus includes numerous species, 

 for the most part known only by their dental plates, and has a 

 remarkably wide distribution in different geological formations. 

 Species occur in the Trias of England, Germany, India, South 

 Africa (Upper Karoo strata), and also, but more rarely, in certain 

 Jurassic deposits in England and in Colorado. 1 Neoceratodus 

 is represented by a solitary species, N. forsteri 2 (Fig. 304, A), 

 which is now restricted to the Burnett and Mary rivers in 

 Queensland. A somewhat wider . distribution of the species in 

 recent times is indicated by the presence of teeth in the later 

 Tertiary (alluvial) deposits of Darling Downs, near the borders 

 of New South Wales. 



The Neoceratodus 3 of the Burnett frequents the comparatively 

 stagnant pools or water-holes which alternate with shallow runs 

 and are usually full of water all the year round. In these pools, 

 filled with a rich growth of aquatic vegetation, and often the 

 favourite haunt of the Platypus (Ornithorhynckus), the Fish is 

 fairly abundant. Inactive and sluggish in its habits, usually 

 lying motionless on the bottom, the Fish is easily captured by 

 the natives with hand-nets or baited hooks. Neoceratodus lives 

 on fresh-water Crustaceans, worms, and molluscs, and to obtain 

 them it crops the luxuriant vegetation of the water-holes much 

 in the same way that a Polychaet or a Holothurian swallows 

 sand for the sake of the included nutrient particles. Apparently 

 the air-bladder is a functional lung at all times, acting in con- 

 junction with the gills. At irregular intervals the Fish rises 

 to the surface and protrudes its snout in order to empty its lung 

 and take in fresh air. While doing so the animal makes a peculiar 

 grunting noise, " spouting " as the local fishermen call it, which 

 may be heard at night for some distance, and is probably 

 caused by the forcible expulsion of air through the mouth. 

 Useful as the lung is as a breathing organ under normal con- 



1 Miall, Palaeont. Soc. 1878 ; Teller, " Ueber Ceratodus sturi," Abh. k. k. Geol. 

 Reichsanst. "\Vien. xv. 1891. 



2 Giinther, Phil. Trans. 161, 1871, p. 511. 



3 Senaon, Zool. Forsch. im Australicn, i. Jena, 1893, p. 13 et seq. 



