286 FISHES 



of 20 fathoms and at a depth of 200 or more, but some species 

 are known to have a very wide range of depth, which may be 

 horizontal in bottom fishes or vertical in free-swimming forms. 

 The greater part of the great oceans, the Atlantic, Pacific, and 

 Indian, is over 2000 fathoms in depth, and a somewhat smaller 

 portion, especially in the Atlantic, is from 1000 to 2000 fathoms ; 

 the parts over 3000 fathoms are of small extent, and there are 

 only three deep holes off Japan, New Zealand and the West 

 Indies where the depth of 4000 fathoms is exceeded. The 

 greatest depth at which fish have been taken is nearly 3000 

 fathoms, to be precise 2949 fathoms, in the western part of the 

 North Atlantic by the American investigation vessel Albatross, 

 and the fish in question was MelampJiaes beanii, a species of the 

 family Berycida^, the most primitive of the spiny-finned fishes 

 (Acanthopterygians) ; at the same haul was taken Stephanoberyx 

 gillii, a type of a family placed by Boulenger in the Sub-Order 

 Haplomi on account of its abdominal pelvic fins, but resembling 

 the Berycidse in many respects. It would be well to confine 

 the term abyssal to fishes taken at depths of more than 1000 

 fathoms, and to form a separate group for those found between 

 200 and 1000 fathoms. While many families include abyssal 

 members there are some families which are found only in the 

 great depths, and although we have maintained that the most 

 primitive forms are usually inhabitants of fresh water, some of 

 these exclusively deep-sea fishes belong to the primitive soft- 

 finned Sub-Order Malacopterygii, or at any rate show primitive 

 characters, a fact which in the present state of knowledge we 

 do not attempt to explain. 



The Alepocephalidai or Fox-heads belonging to the Mala- 

 copterygii are all abyssal ; there are about thirty-five species 

 distributed in the Atlantic, Pacific, and Indian oceans mostly 

 between 1000 and 2000 fathoms, though they have been taken 

 frequently at less depths and occasionally at greater. They 

 resemble in structure the Clupeidae and Salmonidas. The 

 families Halosaurid?e and Notacanthidae, placed by Boulenger 

 in the Sub-Order Heteromi, are also exclusively found in deep 

 water, but many of the species occur at depths somewhat less 

 than 1000 fathoms; Halosauropsis rostratus, however, was ob- 

 tained by the Challenger in the Atlantic at 2750 fathoms. 

 LipogenySy also from the Atlantic, is closely allied to the 



