184 THE VOYAGE OF H.M.S. CHALLENGEE. 



Habitat. — Off Yedo, Station 237; depth, 1875 fathoms. One specimen, 19 inches 

 long. 



Middle of South Pacific, Station 281 ; depth, 2385 fathoms. One specimen, 7^ 

 inches long. 



This fish is highly interesting, inasmuch as the points in which it difi'ers from 

 Bathysaurus ferox indicate that it is merely an abyssal modification of that species ; or, 

 if the present form were not known to attain to nearly the same size as Bathysaurus 

 ferox, it might have been taken for an earlier stage of the development of the latter. 



The fish is of a whitish colour, the buccal and branchial cavities and the lower parts 

 of the body being black. The bones of the head are less firm than in Bathysaurus ferox, 

 the scales extremely thin and deciduous (only a few are preserved), some parts of the 

 body, as the gill-cover and the prseventral portion of the body, being naked. All the 

 fin rays are prolonged, and a short but high adipose fin is present, as also a broad fold at 

 the root of the caudal fin above as well as below. The greatest depth of the body is 

 below the origin of the dorsal fin and more than twice the depth of the caudal peduncle, 

 one-ninth of the total length, without caudal. The head is less broad than in Bathy- 

 saurus ferox, about one-third broader than deep, and its length is two-ninths of the 

 total, without caudal. Snout depressed and of moderate length ; eye of moderate size, 

 one-half of the length of the snout, one-seventh of that of the head, and two-thirds of the 

 width of the interorbital space. 



Otherwise the configuration of the head as well as the dentition are as in Bathysaurus 

 ferox. The position of the nostrils is likewise similar, but they are separated by a rather 

 long and pointed tentacle, and there is another aperture in front of the nostrils which 

 leads into one of the superficial mucous channels. 



The anterior dorsal rays are much higher than the body underneath, their length 

 being equal to that of the head without snout ; but the position of the finis the same as 

 in Bathysaurus ferox. The adipose fin occupies a position behind the last anal ray; the 

 caudal fin is very broad, deeply emarginate, and without scales on its base. Pectoral 

 with a very narrow base, lateral, subhorizontal, with the middle ray longest, nearly as 

 long as the head. Ventral fin very strong and broad, and with the outer ray enveloped in 

 thick skin ; it is inserted in front of the dorsal and is not much shorter than the pectoral. 



In the young specimen the body and tail are ornamented with fourteen narrow 

 vertical bars, composed of minute pigment spots, and reaching across the whole depth of 

 the body. In the interspaces between them there is a shorter bar which does not extend 

 upwards beyond the lateral line. A pattern of coloration of this kind is of extremely 

 rare occurence in deep-sea fishes. 



The structure of the lateral line is the same as in Bathysaurus ferox. 



This species difi'ers internally from its congener more than one might expect in two 



