186 THE VOYAGE OF H.M.S. CHALLENGER. 



Habitat. — Near the Kermadec Islands, Stations 170, 170a; depths, 520 and 630 

 fathoms. Two specimens, 13 inches long. 



The form of the body of this singular type of fishes is somewhat elongate, moderately 

 compressed; its greatest depth is below the origin of the dorsal fin and equals one -sixth of 

 the total length, without caudal. The head is broad, composed of solid bones, about as deep 

 as wide, and terminates in a long, depressed, wedge-shaped snout. The eye is minute, 

 two-thirds as distant from the extremity of the snout as from the hind margin of the 

 gill-cover. Interorbital space very broad, osseous, convex, with a width equal to the 

 length of the snout. 



The bones composing the jaws are very powerful and firm, thus compensating for the 

 weakness of the dentition, which consists merely of a narrow band of villiform asperities 

 in the jaws and of a similar patch on each side of the vomer. The intermaxillary alone 

 is toothed, styliform, tapering and closely fitting into the front margin of the maxillary ; 

 the latter is toothless, about half as long as the head, and its hinder portion, which extends 

 beyond the intermaxillary, is dilated into a broad and oblong lamella. When the mouth 

 is closed, the maxillary occupies a horizontal position in ab.out the middle of the depth 

 of the head, and extends beyond the middle of its length. The lower jaw is extremely 

 broad, its halves touching each other below, when the mouth is shut. Its symphyseal 

 portion forms a strong and large projection. 



Branchial apertures very wide, extending forwards to the end of the isthmus, the gill- 

 cover remaining entirely free. There are four gills with well-developed gill-laminss. 

 All the branchial arches are provided with gill-rakers, but those of the outer arch are the 

 longest and those of the inner the shortest. The outer arch has thirty gill-rakers in its 

 low^er branch and twelve in its uj^per ; they are slender, needle-shaped, the longest about 

 one-fourth of the length of the head. 



The dorsal fin occupies exactly the middle between the extremity of the upper jaw 

 and the root of the caudal fin ; it is much higher in front than behind, the anterior rays 

 being rather higher than the body underneath. Adipose fin narrow, nearly midway 

 between the dorsal and caudal. Anal fin opposite to the space between the dorsal and 

 adipose. Caudal fin emarginate. Pectoral fin lateral, placed in the middle of the 

 height of the trunk, and composed of exceedingly elongate and simple rays, which are 

 quite free, not connected by membrane; the longest reach to the end of the anal 

 fin. An exceedingly long and compressed ray is detached from the fin and articu- 

 lated at the upper end of the clavicle, opposite to the upper margin of the gill-cover. 

 It extends far beyond the caudal fin and is bifid in its posterior half; it is accompanied 

 below by two other rays, which are much shorter and connected by a membrane 

 with the long ray. By a separate set of muscles (PI. XLVIII. fig. B') it can be moved 

 outwards or upwards (c) so as to form nearly a right angle with the longitudinal axis of 



