228 FISHES OF AUSTRALIA. 



shaped body and pass through a number of remarkable 

 changes with age, the young being quite unlike the adult. 

 The former has large, strong spines upon its body, while 

 the latter is quite smooth. Their jaws are undivided in the 

 middle, comparatively feeble, but well adapted for masti- 

 cating their food, which consists of small pelagic crusta- 

 ceans, jellyfishes and larval fishes. The Common Sun-Fish 

 (Mola mola), which has been taken on the coast of New 

 South Wales and other portions of the Australian coast, 

 attains to a very large size, measuring not far short of ten 

 feet and weighing 1800 pounds. It has been observed to 

 swim slowly about near the surface, the high dorsal fin above 

 the water. 



LUNG-FISHES. 



(Sub-class: DIPNEUSTI or DIPNOI.} 



BEFORE passing on to take a cursory glance at the Sharks 

 and Rays, I feel it incumbent upon me to dwell for a little 

 upon the highly-interesting Lung-Fishes. These have 

 earned the common name here applied to them, because of 

 the curious fact that the air-bladder is transformed into a 

 simple kind of lung; so that we here find in these fishes, 

 rather wonderful beings that are able to breathe either 

 water or air. A peculiarity of external structure is that 

 their paired fins give one the impression of being more like 

 simple limbs than fins. 



Lung-Fishes come of a very ancient stock ; fishes re- 

 lated to those at present existing, having lived in some of the 

 waters of the earth even as far back as palaeozoic times. The 

 existing kinds are referred to three genera; known respec- 

 tively as Neoceratodus, Lepidosiren and Protopterus; repre- 

 senting three distinct families, the first being found in 

 Australia (Queensland), the second in South America, and 

 the third in Africa. 



Though all of the species belonging to these three 

 genera agree with one another in some general characters, 

 they differ very considerably in detail ; but I must here con- 



