306 FISHES. 



the surface in the cold and temperate zones, or which appear 

 as nocturnal pelagic forms. The Chondropterygians are few 

 in number, not descending to a depth of more than 600 

 fathoms. The Acanthopterygians, which form the majority 

 of the coast and surface faunas, are also scantily represented ; 

 genera identical with surface types are confined to the same 

 inconsiderable depths as the Chondropterygians, whilst those 

 Acanthopterygians which are so much specialised for the life 

 in the deep sea as to deserve generic separation, range from 

 200 to 2400 fathoms. Three distinct famihes of Acanthop- 

 terygians belong to the deep-sea fauna, viz. Trachypteridce, 

 Lophotidce, and Notacanthida: ; they respectively consist of 

 three, one, or two genera only. 



Gadida\ O^^hidiida;, and Macruridce are very numerous, 

 ranging through all depths ; they constitute about one-fourth 

 of the whole deep-sea fauna. 



Of Physostomi, the families of Stcrno'ptycliidm, Scopelida^, 

 Sto7)iiatid(v, Salmonida\ Bathythrissidce, AlcpoccpJialidcc, Halo- 

 sauridce, and Murainidce are represented. Of these the Scope- 

 loids are the most numerous, constituting nearly another 

 fourth of the fauna. Salmonidm are scarce, with three small 

 genera only. BathytliHsddm include one species only, which 

 is probably confined in its vertical as well as horizontal range ; 

 it occurs at a depth of about 350 fathoms in the sea of Japan. 

 The Alcpoccphalidcc and Halosauridw, known before the 

 " Challenger " expedition from isolated examples only, prove to 

 be true, widely-spread, deep-sea types. Eels are well repre- 

 sented, and seem to descend to the greatest depths. 



Myxine has been obtained from a depth of 345 fathoms. 



It will be useful to append a complete list of Deep-sea 

 fishes, with the depths as ascertained by the dredgings of 

 the " Challenger : " — 



