REPORT ON THE DEEP-SEA FISHES. 207 



branch of the outer branchial arch, where they are remarkably short ; gill-rakers in 

 quite a rudimentary condition. 



The barbel is of nearly uniform thickness, and scarcely more than half as long as the 

 head ; it is inserted somewhat behind the anterior extremity of the hyoid bone, and 

 seems to have terminated in a short, small, black lobe. 



The vent is placed very far backwards, its distance from the root of the caudal not 

 much exceeding that between the pectoral fin and the end of the snout. The anal 

 commences immediately behind the vent, and its depth, as well as that of the dorsal, is 

 less than that of the tail between these two fins. The dorsal fin is shorter than the anal, 

 commencing a little behind, and terminating in front of, the anal. Caud^il short, cleft 

 with pointed lobes. Pectoral very narrow, its upper ray is separate from the remainder 

 of the fin, and produced into a very long and exceedingly fine filament, which nearly 

 reaches the ventral. Ventrals very narrow, pointed, and somewhat longer than the 

 head ; the distance of their base from the end of the caudal equals that from the root of 

 the pectoral. 



The luminous organs ^ are arranged thus : — 



a. A series of rather small, but distinctly developed eye-like bodies begins on the 

 isthmus, and runs along each side of the abdomen to the commencement of the anal fin ; 

 it consists of eight in front of the pectoral, twenty-nine between pectoral and ventral, 

 and fifteen between ventral and anal. 



6. A parallel series, beginning above the root of the pectoral, and running below 

 the median line of the side of the body along the base of the anal to the root of the 

 caudal. The position of the organs corresponds to that in series a ; but there are twelve 

 additional posterior ones, from the commencement of the anal to the root of the caudal. 



c. A series of similar organs along the base of the branchiostegals. 



d. Innumerable smaller, and partly quite rudimentary, organs are scattered between 

 the principal series ; they extend upwards on the sides to the back, but they are there 

 more regularly arranged, a biserial row corresponding to each myocomma. A great 

 number of rudimentary organs, hke raised pigment-spots, are scattered all over the head. 



e. An isolated eye-like organ, larger than any of the others hitherto described, 

 occupies the suture between operculum and suboperculum. 



/ The principal luminous organ, situated behind the eye, along the maxillary, is of 

 a narrow cuneiform shape, pointed behind, and longer than the eye ; it is said to be 

 rose-coloured during life. 



Colour, uniform black. 



Habitat. — Very rare at Madeira, where the only specimen I have seen was obtained ; 

 it is 9 inches long. Another example is reported to have been taken ofi" the coast of 

 Massachusetts. 



1 The result of their histological examination will be given in Appendix B. 



