240 



THE VOYAGE OF H.M.S. CHALLENGER. 



of that of the snout. Eye rather small, one-fourth of the postocular portion of the 

 head, and two-thirds of the width of the interorbital space. Maxillary reaching to the 

 front margin of the eye. The length of the head is nearly twice its distance from the 

 root of the ventral, which is situated almost entirely in advance of the dorsal. Pectoral 

 fin with very narrow base, extending nearly to the root of the ventral. Nearly all 

 the scales are lost, but those of and below the lateral line are much larger than the 

 others, each bearing a luminous organ. 



Distance of the snout from the mouth, . . ... 4 lines. 



Distance of the snout from the eye, 



Distance of the snout from the root of the pectoral fin, 



Distance of the snout from the root of the ventral. 



Distance of the snout from the origin of the dorsal fin, 



Distance of the snout from the vent, 



Total length, ..... 



Habitat. — West of the Philippine Islands, Station 207 ; depth, 700 fathoms. One 

 specimen, 171 inches long. 



The entire head is naked, only the uppermost portion of the giU- cover and the 

 upper half of the cheek are covered with scales similar to those of the body ; the bones 

 of the head are very thin, especially the gill-covers, which are nearly membranaceous, the 

 operculum folded and the other parts striated. The lower half of the side of the head 

 from the snout to the gill-opening is occupied by two exceedingly wide muciferous 

 channels, of which one takes its origin on the preeorbital, the other on the mandible. 

 The nostrils are small openings, close together in front of the eye. 



The dentition is very much like that of Halosaurus macrochir, but the pterygoid 

 band is rather broader. Also the branchial apparatus does not differ from that in the 

 species named. 



The luminous organs are constructed and arranged as in Halosaurus macrochir; 

 the glandular patch being narrower and much deeper, occupying the whole width of the 

 scales, and being pointed above and below. These scales are very large, twice the size 

 of the others and somewhat distantly placed. There are probably no more than 

 eighteen between the gill-opening and the vent. This species is rather light coloured, 

 but the deep black of the buccal and branchial cavities shines through the thin integu- 

 ments ; also the posterior part of the anal fin is black. 



