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



The eye-like phosphorescent organs are small and arranged very much in the same 

 manner as in Scopelus engraulis, but owing to the condition of the specimen no exact 

 description of their number can be given. A long, linear, glandular organ of white 

 colour occupies the back and opposite side of the posterior half of the caudal peduncle. 



Coloration uniform black. 



Habitat. — South of Philippine Islands, Station 214 ; depth, 500 fathoms. One 

 specimen, 4i inches long. 



Odontostomus, Cocco. 



Body oblong, compressed, naked ; head compressed, snout short ; cleft of the mouth 

 very wide ; intermaxillary and maxillary bones slender, the former with a series of small 

 teeth of equal size which have their points directed backwards ; the lower jaw, the vomer 

 and the palatine bones armed with a few very large curved and lanceolate teeth, which 

 are barbed at the tip, curved, and depressible backwards. Eye very large, with the 

 orbital cavity expanded downwards, so that the eye can be turned either upwards or 

 towards the side of the head. Pectoral and ventral fins well developed, the latter are 

 inserted below the dorsal at some distance behind the pectoral. Dorsal fin in the middle 

 of the length of the body ; adipose fin small, placed far backwards ; anal fin long ; 

 caudal forked. Branchiostegals eight ; pseudobranchise well developed, gills four ; the 

 outer branchial arch with small gill-laminaj and without gill-rakers. 



Odontostomus hyalinus, Cocco (PI. LII. fig. A). 



D. 12. A. 34. P. 12. V. 9. 



The height of the body is contained six times and one-third in the total length, 

 without caudal, the length of the head four times and a half. The wide cleft of the 

 mouth, which is oblique, extends far beyond the eye, but does not reach the angle of the 

 prajoperculum. The mandible is broad, not attenuated in front, and projects beyond the 

 mouth. The large fangs can be depressed backwards, and are always depressed when 

 the mouth is closed ; they are very much compressed and sharp-edged in front and 

 behind. The longest of tlie palate have their extremities curiously bent forward. 



The form and structure of the orbit is quite unique ; it is, in fact, turned upwards, 

 separated from its fellow by an extremely narrow interorbital space ; its lateral wall is 

 formed by a transparent membrane so that the fish Ijy rotating the eye-ball behind this 

 membrane outwards for 90°, can place the eye in the usual position on the side of the 

 head, and thus see either sidewards or upwards. The infraorljital ring is very narrow, 

 Ijent in a strong curve, within which the transparent orbital membrane is extended. 



