"PERFECT-MOUTHED" FISHES 239 



appearance of the dory seen in this way is a mere line in the water, 

 to which no particular significance can be attached." Slowly and 

 deliberately the dory moves towards its victim, on which its 

 eyes are fixed with intense excitement ; then, when it has drawn 

 near enough to the desired object, the tube-like jaw is shot out 

 and the victim seized. The dory is common in the Bristol and 

 English Channels, and is often taken in the trawls on the coasts 

 of Cornwall and Devon. 



The Boar-fish, which belongs to the dory family, is also fairly 

 abundant on the south coast in the summer months. It is a 

 small fish, with a greatly compressed body and the characteristic 

 tube-like mouth, and is of a brilliant pink colour. This fish may 

 sometimes be found stranded on the shore as the tide is retreat- 

 ng, and is said actually to flop its way out of the water again 

 if thrown back into the sea. 



It is not at all uncommon to find fishes left behind by the tide 

 on sandy, shelving shores ; on the Scandinavian coasts the curious 

 Ribbon-fish (Trachypterus arcticus) is often cast up by the waves 

 at flood-tide. Ribbon-fishes are remarkable for their long, ribbon- 

 like bodies; the dorsal fin extends from head to tail, the front 

 portion standing erect like a crest. The mouth is tube-like and 

 very protractile, like the mouth of the dory and boar-fish. The 

 Northern Ribbon-fish reaches a length of about 8 feet, and the 

 Oar-fish (Regalecus glesne), an allied species, is sometimes over 

 20 feet long. This great fish, which swims with undulating move- 

 ments, holding the top of its head and crest above the water, is prob- 

 ably the " sea-serpent " of which we hear from time to time. 



The Lung- fishes, or Dipnoi, usually called " Mud-fishes," are 

 an old tribe of fishes of which there are now only a few living 

 representatives found in certain rivers in Africa, South America, 

 and Australia. On account of certain peculiarities of structure 

 they are separated by zoologists from all other fishes, and placed 

 in a division or sub-class by themselves. The most distinctive 

 characteristic of these fishes is indicated by their name Dipnoi, 

 which means " double-breathers," for, as already stated on page 206, 

 in addition to the ordinary fish-like gills, they possess a highly de- 

 veloped apparatus or "lung" for breathing atmospheric air after 

 the manner of land animals. In some species the lung is single ; 

 others have a pair of lungs united in front. The fishes are 



