416 FISHES 



organ above the edge of the upper jaw on each side and the 

 usual series near the ventral edge of the body. One specimen 

 was taken by the Challenger in the middle of the Atlantic at 

 the depth of 2750 fathoms, but two specimens had previously 

 been obtained at the surface to the north of New Guinea ; in this 

 case, however, there can hardly be any doubt that the fish is 

 really bathybial and lives near the bottom. 



The Alepocephali are a family of bathybial fishes allied to 

 the Clupeidas and Salmonidse ; some of the members are scaled 

 and in most of these luminous organs are absent, but in the 

 scaleless forms the skin, at least in some species, bears scattered 

 small projecting nodules which have the appearance and structure 

 of such organs. One of these species is called Xenodermichthys 

 nodulosus, and a single specimen was taken by the Challenger 

 south of Japan at a depth of 345 fathoms. Aleposomus socialis is 

 another species of which large numbers of specimens were taken 

 in the French expedition of the Talisman off the west coast of 

 Africa at a depth of about 600 fathoms. It has spots, probably 

 of the same nature as those of Xenodermichthys, on the head 

 and anterior part of the body. 



There is, however, some reason to conclude that deep-sea 

 fishes may be luminous even when they possess no special light- 

 organs. Alepocephalus affinis, for instance, taken from a depth of 

 753 fathoms off the Kistna coast in the Bay of Bengal, is de- 

 scribed by Lt.-Col. Alcock as being quite black in colour and 

 having its skin everywhere covered with a thick opalescent epi- 

 dermis which was uniformly luminous ; he states that the only 

 specimen captured glimmered like a ghost as it lay dead at the 

 bottom of a pail of sea-water. The glimmering of a ghost is 

 not a phenomenon authenticated by any scientific evidence, but 

 the observation that the surface of the fish glimmered although 

 no special light-organs were present is of considerable scientific 

 interest. 



The Halosaurid?e are fishes with strongly marked char- 

 acters placed by Boulenger with the parasitic Fierasferidae and 

 a few other families in a separate suborder, the Heteromi. 

 Their affinities are not very certain. They have a pointed 

 snout projecting beyond the jaws, a single short dorsal fin 

 about midway between snout and anal region, a long caudal 

 region tapering to a point without distinct tail-fin, and a long 



