20 THE VOYAGE OF H.M.S. CnALLENGER. 



greater propriety than Lophotes. The specimen is only 1 1 ram. long and much 

 distorted; it was obtained in April 1875 on the passage from the Admiralty Islands to 

 Japan. It resembles much the adult form in the shape of its head and in the structure 

 of its fins ; the characteristic long and powerful dorsal ray is present though unfor- 

 tunately broken off", only its basal portion being preserved. The chief diff'ei-ence from 

 the adult is the proportion of the length of the body to that of the head, the body 

 being much less elongate and the head only about two-sevenths of the total length. 

 Diff"erences of minor importance seem to be the position of the anterior dorsal ray, the 

 root of which is somewhat behind the foremost part of the upper profile, and also the 

 absence of the ventral fin, which may have been accidentally destroyed. 



The embryonic condition of our specimen is clearly shown in the termination of the 

 tail, which is heterocercal, a condition of which the last trace is indicated in the adult 

 by the lateral line ending at the base of the upper, and not of the middle, caudal rays. 

 In the dorsal fringe, as also in the other vertical fins, the rays are visible as minute and 

 densely packed fibres. 



The dorsal fringe surrounds the end of the notochord and is continuous with the 

 portion (c) which, with growth, would be diff"erentiated as the caudal fin, and in which 

 the fibres are stronger and longer. The anal fringe («) is separated from the caudal by 

 the integument; a fringe {joa) similar to the anal exists in front of the vent (f), and runs 

 for a short distance along the median line of the abdomen. 



The fish is of a silvery colour, with pigment spots on the head, and others serially 

 arranged along the terminal portion of the notochord. 



Fig. K' represents the posterior end of the body much enlarged. 



III. ANACANTHS. 



Onus reinhardtii, CoUett (PI. III. fig. F.). 



Adult specimens of this species were obtained by the " Knight Errant " in the 

 Fseroe Channel at a depth of 540 to 640 fathoms in 1880.* Two years later three 

 young specimens, referable to the same species, were caught at the surface by the 

 "Triton" (August 9, 1882). They have the compressed body of the Couchia-stage of 

 this genus, and are silvery, with a green back. Their fin-formula I make out to be — 

 D. 52. A. 45. P. 20. V. 8. The greatest depth of their body is one-seventh of the 

 total length, the length of the head a little less than one-fourth. The eye is one-fourth 

 of the length of the head and equal to the length of the snout, this portion of the head 

 being more pointed and more projecting beyond the lower jaw than in the young of the 



' See Report on Deep-Sea Fishes, Zoul. Chall. Exn., pt. Ivii. p. 98. 



