88 FISH GALLERY. 



and subtropical seas. Their usual length is about 10 or 12 inches, 

 but specimens of 18 inches have been caught. They are enabled to 

 execute flying leaps by means of the great development of their 

 pectoral fins. They dart out of the water when pursued by their 

 enemies, or frightened by an approaching vessel, but frequently also 

 without any apparent cause, as is also observed in many other 

 fishes; they rise without regard to the direction of the wind or 

 waves. During flight the fins are kept quietly distended, without 

 any motion, except an occasional vibration caused by the air when- 

 ever the surface of the wing is parallel with the current of the 

 wind. Their flight is rapid, greatly exceeding that of a ship going 

 10 miles an hour, but gradually decreasing in velocity, and rarely 

 extending beyond a distance of 500 feet. Flying-fishes often 

 fall on board of vessels ; but this never happens during a calm, or 

 from the lee side, but during a breeze only, and from the weather 

 side. 

 [Case The Osteoglossida (Case 22 b) are large freshwater fishes of the 



22 b."] tropics. Of the genus Osteoglossum three species are known — one 

 from Brazil and the Guianas, one from Borneo and Sumatra, and the 

 third from Queensland. The single species of the genus Heterotis 

 (H. niloticus) is not uncommon in the Upper Nile and the West- 

 African rivers. The genus Arapaima (fig. 75) also contains a 

 single species, A. gigas (exhibited in separate table-cases), from the 

 rivers of Brazil and the Guianas, and highly esteemed as an article 

 of food. It is the largest freshwater Teleostean known, exceeding 

 a length of 15 feet, and a weight of 400 lb. 



.-■-.- 



Arapaima of the River Amazon. 



[Case The Clupeidce, or Herrings (Case 22 b), are probably unsurpassed 



L-J J by any other family in the number of individuals, although others 



comprise a much greater variety of species. The Herrings are 



principally coast-fishes; none belong to the deep-sea fauna; 



