CHAPTEE XX. 



DISTRIBUTION OF PELAGIC FISHES. 



Pelagic Fishes, — that is, fishes inhabiting the surface of mid- 

 ocean (see p. 255), belong to various orders, viz. Chondrop- 

 terygians, Acanthopterygians, Physostomes, Lophobranchs, 

 and Plectognaths. But neither Anacanths nor Pharyngog- 

 naths contribute to this series of the Marine Fauna. The 

 following genera and families are included in it : — 



Chondropterygii: Carcharias, Galeocerdo, Thalassorhinus, 

 Zygpena, Trii^^nodon, Lamnida;, Ehinodon, Xotidanidne, Lcemar- 

 gus, Euprotomicrus, Echinorhinus, Isistius ; Myliobatida^. 



AcANTHorTERYGii : Dactyloptei'us, Micropteryx, Scom- 



brina, Gastrochisma, Nomeus, Centrolophus, Corj^phsenina, 



Seriola, Temnodon, Xaucrates, Psenes, Xiphiidaj, Antennarius. 



Physostomi : Sternoptychida^, Scopelus, Astronesthes, 



Scombresocidffi (majority). 



LoPHOBRANCHii : Hippocampus. 



Plectognathi : Orthagoriscus, and some other Gymnodonts. 

 Pelagic fishes differ much from one another in their mode 

 of life. The majority are excellent swimmers, which not only 

 can move with great rapidity, but also are possessed of great 

 powers of endurance, and are thus enabled to continue their 

 course for weeks, apparently without the necessity of rest : 

 such are many Sharks, Scombroids, Dolphins, Pilot-fish, Sword- 

 fishes. In some, as in Dadylopterus and Exocoetus, the ability 

 of taking flpng leaps out of the water is superadded to the 

 power of swimming (Flying-fishes). But in others the power 



