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.  Neoceratodus 
is represented by a solitary species, V. forsteri” (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* 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 (Ornithorhynchus), 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. Meoceratodus 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. Wien. xv. 1891. 
2 Giinther, Phil. Trans. 161, 1871, p. 511. 
3 Semon, Zool. Forsch. im Australien, i. Jena, 1893, p. 13 et seq. 
