IV. GEOGRAPHICAL DISTRIBUTION. 



Though the details of the distriliution have already been given under each species, it 

 is desirable that a few lines should be devoted to a consideration of (1) the distribution of 

 the genus, and of the relations of the species, so far as regards their distribution, to each 

 other ; and (2) the factors that have caused, or at least aided, in bringing about the 

 distribution. 



HALOBATES. 



Willlerstorffi is the most widely diffused species. It is pre-eminently the species of the 

 North Atlantic, and occurs also in the South Atlantic, Indian, and West Pacific Oceans. 



Micans is reported from the Atlantic, Indian, and Pacific Oceans, but seems to be very 

 rare, and it is possible that some confusion exists in the records, and that wullerstorffi has 

 in some cases been confounded with micans. 



Sericeus is a species that seems very abundantly represented Ijy individuals, but it is 

 almost confined to the Pacific, especially the North Pacific, of which it is pre-eminently 

 the species. It has been recorded as occurring near the Cape and near Madagascar, but 

 this is possibly an error of determination. I have before me two specimens (from the 

 Challenger) from the North Atlantic. I cannot think that there is a mistake about 

 the locality of these, but still, corroboration is very desirable. 



Flavivent7-is is a rare species. I have seen specimens from near St. Helena, and fi-om 

 near Ceylon, and it has also been reported from near Madagascar. 



All the remaining species are, so far as we yet know, very limited in their distribution. 



Streatjieldanus has only once been taken in the South Atlantic; huyaiius occurs at 

 Aden ; frauenfeldanus at the Nicobars ; proavus near Gilolo ; 2:trinceps in the Celebes Sea ; 

 and germanus and sohrinas in one or two localities in the Pacific. 



To sum up, five species occur in the Atlantic, but one only is (so far as we know) 

 restricted to that ocean, though the headquarters of another appear to be there. 



Six species, of which two are peculiar, occur in the Indian Ocean, west of long. 100° E., 

 while to the east of long. 100° E., and chiefly in the West Pacihc, eight species occur, of 

 which four are restricted to that region. But if we take the Indian Ocean and West 

 Pacific together, we find that nine out of the eleven known species occur there, and five 

 nowhere else. It would seem, therefore, that the region between the eastern part of the 

 Indian Ocean and the West Pacific is the metropolis of the genus, and it does not seem to 



