PELAGIC FAUNA 



85 



a pair of fixed, upturned binoculars. The fish has large, 

 thin scales and its belly is as flat as the sole of a shoe. 

 Gigantura also has telescopic eyes. Unlike most other fishes, 

 it can see with both eyes at once. Gigantura is also notable 

 for its extremely elongated tail-fin, as well as for its ability 

 to swallow enormous prey. Another strange fish is Style- 

 phorus (Fig. adjoining), which is related to the deal-fish ; its 

 binoculars can be turned both upward and forward. This 

 is a silvery, ribbon-shaped fish, the two bottom rays of the 

 caudal fin being elongated into an immensely long thread 

 which may be twice as long as the fish's body. The large 

 eyes are forwardly directed. But the strangest feature of all 

 is the mouth. This is small and toothless, but can suddenly 

 be thrust right forward, when the whole facial appearance 

 will change simultaneously, so that the eyes turn upward 

 instead of forward. All these and many more fishes were 

 found on the expedition. 



An unusually ferocious appearance is presented by the 

 angler-fishes, a strange group in more ways than one. Some, 

 like our common angler, Lophius piscatorius, are bottom- 

 dwellers; and a wide range of small species live in the 

 Sargasso weed which drifts about on the surface of the 

 oceans. The bathypelagic angler-fishes (Ceratioidea) form 

 a special sub-order comprising nearly a hundred species. 

 Most of these are small, short, and plump and have only a 

 small tail, their swimming powers being rather poor. They 

 are black and scaleless, and they have small gill-slits and 

 small, almost rudimentary eyes. The jaws are huge with 

 many long, spiky teeth which can be folded back when the 

 mouth is closed. The stomach is very distensible. They have 

 a stalky light organ (a transformed fin ray) on the nose, 

 and a few also have a luminous chin-barbel. They occur 

 most frequently at depths below 2,000 metres, though 

 young individuals may be found at higher levels. They in- 

 habit all the oceans, but predominantly the tropical and 

 subtropical zones. In these dark depths it may be difficult 

 for the sexes to find each other, a problem which the deep- 

 sea angler fishes have solved in a very remarkable way, 

 unique among fishes. While quite small, the male fish 

 grips some random part of the female with its jaws. Some- 





A deep-sea fish (Stylephorus) 

 which swims with its head up and 

 tail down. The figure on the left is 

 greatly reduced to show the full tail 

 filament. Inhabits depths of 200- 

 400 metres. 



