302 DEEP SEA FISHES. 



ventrals, more than lialf as long as the head. Caudal most often with six 

 rays ; occasionally there are but five, and in one case there are ten. In 

 this last instance shortness of dorsal and anal indicate a mutilation similar 

 to that so frequently met with in the Macruridse. The bifid maxillary with 

 its sjaine makes an approach toward the Halosauridas that demands the addi- 

 tion of this feature to those already mentioned by Alcock, 1889, Ann. Mag. 

 N. H., IV, 455, as suggestive of affinities between Halosaurichthys and Nota- 

 canthus, " the dorsally keeled tail with its indurations, the united ventrals, 

 and the loose palatine bones." Scales minute, thin, adherent, cycloid, cover- 

 ing head and body. Lateral line distinct, on the upper half of the flank, 

 about twentj^-four scales from the origin of the dorsal, or twice as many 

 from that of the anal, absent on the tail for about one fourth of the total. 

 Five pyloric appendages. 



On the largest specimen the color is rusty brownish red, tinted with 

 bluish ; blackish on the opercles and on the linings of the mouth and the 

 body cavity. Smaller individuals are liglit brownisli red. 



Total leno-th ten inches. 



The families included by this group exhibit a large amount of diversity 

 in form and structure and this is accompanied by a considerable variety 

 in habits. Nearly all of the species live at the bottom. Burrowing in the 

 mud and more or less nocturnal the MurEenoids have descended and adapted 

 themselves readily to the conditions of life at great depths and from the 

 consequent plasticity, brought about by reduction of the amount of inor- 

 ganic materials and of firmness in the structure, thus bringing the adult and 

 the aged in a measure to resemble the young or the embryo of the surface 

 forms in flexibility and presumably in susceptibility to modification, they 

 have become, through conscious and through unconscious efforts to adapt 

 themselves to or to protect themselves from the demands of their changed 

 circumstances, possessed of diversifying tendencies that have produced some 

 of the strangest forms among the fishes. That the fishes of great depths 

 are rather more subject to variation than those near the surface is the con- 

 clusion one reaches from a study of bathybial species. The parasitic habit, 



