FISHES. 321 
mallet. Some are as broad as long; some unusually thin, with 
scarcely a difference between their head and tail, while their gills 
THE HAMMER-HEADED SHARK. 
(Zygena tudes.) 
are not unlike the holes in a flute. Then there is as much diversity 
as can possibly be imagined in their scales—they are of all shapes, 
THE TRIANGULAR TRUNK-FISH. 
(Ostracion trigueter.) 
sizes, and colours. They vary from a point to a plate; but are 
always placed symmetrically, and generally overlying each other 
like the tiles of a roof. The skin of the fishes is always lubricated 
V 
