FISHES FROM THE SEA-BOTTOM 415 



Halosaurus, and the two Synaphobranchidse may be suspected of 

 pelagic habitat. Less doubt may be entertained about the 15 

 Macruridae and the 8 Zoarcidae, and the probability is that these 

 (some 20 individuals) constitute the total result of the attempts 

 of all the deep-sea expeditions to capture bottom-fish on the 

 abyssal plain beyond the 2000-fathoms line. Most of these 

 fishes were taken by the "Challenger" in 57 hauls with the 

 dredge or trawl in depths exceeding 2000 fathoms. In these 

 hauls 22 individuals were captured, and the French expeditions 

 caught 1 1 bottom-fish in eight hauls, giving an average of i 

 fish to two hauls. 



The 35 individual fishes enumerated belong to 21 species, 

 15 genera, and 6 families. On the average not even two 

 individuals of each species have been captured. The genus 

 Macrurus preponderates, 15 of the 35 individuals belonging to 

 this genus, and of deep-sea fishes the Macruridae may most 

 safely be regarded as bottom-dwellers. The impression of Scantiness of 

 scantiness conveyed by these facts, only one or two individuals greTdepOis.^ 

 of each species of fish being known from the immense area of 

 the abyssal plain, agrees with the scarcity of the lower orders 

 in the same barren region. A perusal of the "Challenger" 

 Reports astonishes us by the fact that large numbers of species 

 of lower animals are known only from a single locality, and 

 often from one solitary specimen. 



These facts suggest that the bottom-fishes of the abyssal 

 region are very local in their occurrence, but, considering the 

 small number of individuals recorded, it seems risky to come to 

 that conclusion, as the want of material for comparison tends to 

 weaken our power of discriminating between the species. In 

 certain problems of geographical distribution, the question may 

 be vital whether two individual fishes caught in widely separated 

 parts of the world are to be referred to one species or not. 

 The systematic study of these deep-sea species leaves a strong wide dis- 

 impression that many of them differ very slightly from one Jj^^p!^"^ °^ 

 another. Thus, for instance, my collaborator, Mr. E. Koefoed, forms. 

 and myself have not been able to convince ourselves that there 

 is any specific difference between the two species, Macrurus 

 armatus and M. gigas, mentioned in the above table, and this 

 circumstance alone leads to far-reaching conclusions, M. armatus 

 having been caught in the Pacific and M. gigas in the North 

 Atlantic (see Fig. 308). 



The collections of the " Michael Sars " throw much new 

 light on these questions. In the following table I give the 



