226 FISHES OF AUSTRALIA. 



The teeth, in these fishes, are welded together to form 

 two powerful crushing plates in each jaw. From that 

 character the generic name of Tetrodon (which includes a 

 large number of Toad-Fishes), meaning "four-teeth," is 

 derived. 



The Toad-Fish illustrated (Tetrodon lavigatus) is a 

 very widely distributed species. ' 



In America the fishes of this family are often termed 

 "Rabbit-Fishes" on account of their peculiar teeth, and also 

 occasionally the rabbit-like head. 



SEA-PORCUPINES. 



(Family: Diodontidce.} 



THE Porcupine-Fishes are somewhat similar in many ways 

 to those just mentioned, but they are generally characterised 

 by the presence all over the skin of long and sharp thorns 

 or spines. In some species, such as our common "Porcu- 

 pine " (Dicotylichthys punctulatus) these spines are im- 



D 



Fig. 81. SEA -HEDGEHOG (Diodon hystriac). 



moveable and jut out from bony plates which are set in the 

 skin of the fish ; while in the others, the spines are erectile ; 

 that means that when the fish is not feeling particularly 

 warlike, the spines lie against the body pointing backwards ; 

 but immediately the skin is inflated with either air or water 

 the spines stand straight out all round the fish, making it 

 a really formidable object. Some Porcupine- Fishes are 



