4 8o 



PISCES SUB-CLASS lILTELEOSTOMI. 



ever, much more ordinary-looking fishes than their parents, as the beak is 

 not developed till late in life. During the growth of the beak the lower jaw- 

 is considerably longer than the upper one, although in the fully adult con- 

 dition the two are equal in length. So much has been written about the 

 habits of flying-fish (Exocc&tus), and their form is so familiar, especially to those 

 who have made a voyage in the warmer seas, that we may be well excused 

 from saying much about either point in this place. The only other inhabi- 

 tants of the deep which indulge in similar flights are the flying-gurnards, with 

 which the true flying-fish are not likely to be confounded. To support them 

 in the air, the pectoral fins of the flying-fishes are greatly elongated. In 

 shape they are less elegant than many fishes, the head being blunt and 

 almost truncated in front. There are numerous species of the genus, some 

 of which appear to range over all seas suited to their existence, while others 

 have a curiously circumsuited habit. A foot is about the usual maximum 

 length, although specimens of eighteen inches are from time to time met 

 with. 



Flying-fish associate in shoals, and when disturbed by a vessel, which they 

 not improbably mistake for a whale, rise one after another from the waves 



like a flock of swallows driven from 

 their shelter. Although it is highly 

 probable that their pectoral fins may 

 vibrate for a few seconds after leav- 

 ing the water, the flight of these 

 fishes is due entirely to the initial 

 velocity of the leap with which they 

 leave the water ; and how great this 

 velocity is, may be inferred from the 

 circumstance that sometimes the flight 

 may cover a distance of at least three 

 hundred yards. Probably attracted by 

 the lights, flying-fish not unfrequently 

 leap on board the deck of small vessels, while they occasionally make their 

 entrance on to those of larger tonnage by way of the open port-holes. 

 On one occasion during a voyage home from South America, such an unbidden 

 visitor entered in this manner the cabin of a passenger, who at the time 

 was shaving, and received a severe blow in the face from the newcomer. 



The next section of the Acanthopterygii is typified by the stickle-backs of 

 our streams and ditches ; and common and familiar as these little fishes are, 

 they are nevertheless highly interesting to the naturalist, 

 both on account of their structure and their habits. Unfor- 

 tunately, in our limited space, little can be here said on 

 either. As a sectional group, the Gastrosteiformes are 

 characterised by the circumstance that when a spiny dorsal 

 fin is present at all, this takes the form of a variable number 

 of isolated spines. Although in some forms the pelvic fins are thoracic, in 

 others they assume an abdominal position, owing to the prolongation of the 

 bones of the pelvic girdle, which are attached to the pectoral arch. The 

 snout is generally more or less produced, with the small mouth at its ex- 

 tremity. It will be unnecessary to characterise the stickle-backs (Gastrosteus) 

 in full, and it will therefore suffice to say that their somewhat compressed 

 and elongate bodies are either naked, or protected by large plates on the 

 sides, and that the number of spines on the back may vary from as few as 



Fig. 14. FLYING-FISH. 



Section Gastros- 

 teiformes. 



Family 

 Gastrosteida. 



