216 THE VOYAGE OF H.M.S, CHALLENGER. 



Known from two specimens in the Berlin Museum ; the larger, about 5 inches 

 long, was obtained north of Australia in long. 117° E., the smaller, 2 inches long, 

 north of New Guinea in lat. 1° 4', long. 136° E., both at the surface. 



Idiacanthus ferox (PI. LII. fig. D). 



Bathyophis ferox, Guntli., Ann. and Mag. Nat. Hist., 1878, vol ii. p. 181. 

 D. 60. A. 45. V. 6. Vert. ca. 69. 



Vent situated at the sixth eighth of the total length. Commencement of the dorsal 

 fin opposite to the root of the ventrals. Black. 



Habitat. — MidtUe of North Atlantic, Station 63 ; depth, 2750 fathoms. One 

 specimen, 8 inches long. 



The body of this extraordinary form is extremely elongate, band-shaped, with the 

 muscular system so little developed, that in its present preserved state the vertebral 

 column appears to be merely covered by the skin, with the outlines of the vertebrse 

 clearly visible. It is one of those deep-sea fishes in which the stomach and the walls of 

 the abdomen are capable of extreme distention, to receive the prey which the fish is able 

 to seize, and to hold with its large and formidably armed jaws. The vent lies at the 

 commencement of the sixth eighth of the total length, the tail being therefore rather 

 short. 



The head is high, compressed, the large jaws forming nearly one-half of its lateral 

 area ; its length is contained thrice and two-thirds in its distance from the ventral fins, 

 or is one-fourteenth of the total length. Eye rather small, not quite twice as distant 

 from the posterior end of the head as from the anterior. Cleft of the mouth extremely 

 wide, extending backwards to the end of the head, slightly oblique, with the lower jaw 

 prominent. The dentition is more complete on the right side than on the left, and 

 consists in the upper jaw of seventeen long and pointed teeth, of which the fourth and 

 the eighth are the longest. The teeth of the lower jaw are still longer, twenty on each 

 side, the fourth and eleventh being very long, whilst the hindmost are very short. 



These teeth when erect prevent the jaws from shutting, but all of them can be 

 depressed to the level of the jaws. Vomer with one or two small teeth on each side, 

 placed at considerable distance from each other ; i^alatine with a series of three or four 

 small teeth, slightly increasing in length backwards ; tongue with three pairs of teeth. 

 Gill-opening very wide, with a very narrow and membranaceous gill-cover. Biirbel long, 

 about twice as long as the bead, with the terminal portion slightly dilated by a narrow 

 fold running along each side, luit the end of the appendage tapers again into a delicate 

 filament (fig. (/). 



The dorsal fin commences opposite to the ventrals, and is composed of widely set. 



