124 DEEP-SEA FISHES OF THE ATLANTIC BASIN. 



Pectorals well developed, close to the lower profile; ventrals small; pelvic bone with 

 a bifid spine in front pointing forwards. The dorsal fin occupies the middle of the back and 

 consists of a triangular bony lamella, very thin in front, but strengthened along its hind 

 margin, and followed by several rays. Adipose fin absent, or represented by a very low 

 membranous fringe of the dorsal margin of the tail. The anal fin is incompletely developed, 

 extending from the vent to the root of the caudal tin, its rays being rudimentary, widely 

 set, and scarcely free. Caudal fin broad and forked. Gill opening very wide, the gill mem- 

 brane being attached to the isthmus. A luminous organ occupies the inner side of the oper- 

 culum close to its end; another is placed at the anterior end of the ceratohyal, and, finally, 

 a very large glandular mass is lodged on the upper edge of the anterior end of the clavicle. 

 GUIs 4; the branchial arches are long, not angularly bent, the branchial slits being closed 

 by a membrane in their upper portion. Only a few of the gill rakers are prolonged, needle- 

 shaped, and widely set, the others being quite rudimentary. Pseudobrauchke present. 

 (Giinther.) 



STERNOPTYX DIATHANA, Lowe. (Figure 146.) 



Stemoptyx diaphana, Hermann, Naturforscher, 1781, xvi, 8, tat'. 1. figs. 1 and 2 (bad), and xvn, 249 (cop. 

 by Walhaum, Artedi, m, tab. 1, figs. 1 and 2. — Blocii, Syst. Ichth. ed. Schneider, 1801, 494, pi. 35). — 

 Cuvier, Regne Aniin. 2nd edit... pi. 13, fig. 1. — Cuviek and Valenciennes, Hist. Nat. Poiss., XXII, 

 415. — Lowe, Proc. Zool. Soc. London, 1843, 85. — GOnther, Cat. Fish. I'.nt. Mus., v, 387; Challenger 

 Report, xxn, 1(59-170, pi. xlv, figs. I), I)'. — Vaillant, Exp. Sei., Travailkur et Talisman, 102. 



Stemoptyx Kermanni, Lacepede, Hist. Nat. Poiss. v, 613. 



Height of tlie body equals distance between extremity of the snout and commencement 

 of the tail. Tail very short. Interorbital space slightly concave. Posterior limb of preoper- 

 culum borders hind part of the orbit, and descends in a very oblique line, terminating in 

 two points. Pectoral fin scarcely reaching to tlie ventrals, which are very small. (Giinther.) 



Radial formula: B. 5; D. 10-12; A. lL'; P. 10; V 3. 



This grotesquely shaped and interesting fish was first discovered in the West Indies in 

 1774 by Hermann. 



It was described by him in 1781 in the Xaturforneher. It was next observed in the 

 mid-Atlantic in August, 1S42, when Lowe obtained a specimen taken between Madeira and 

 St. Marys, the southernmost of the Azores, about 80 miles to the southeast of the latter 

 island, in a calm, smooth sea. It was among the rarest of fishes until the time of the Chal- 

 lenger, which upon its cruise around the world obtained quite a number of specimens in the 

 mid-Atlantic, the Australian seas, and in various places in the South Pacific, and about the 

 same time the vessels of the IT. S. Fish Commission and Coast Survey began to obtain it in 

 the western Atlantic. The manner of its occurrence has been very puzzling. Although 

 two or three specimens were obtained at the surface, they were usually caught up in a 

 dredge or trawl from 500 to 2,500 fathoms, and the peculiarities of its distribution have 

 given rise to much speculation. A study of the list of specimens published in the Chal- 

 lenger Report would seem to indicate that the fish inhabits all depths from the surface 

 downward. Dr. Giinther is unable to accept this as an indication of that state of affairs, 

 and is of the opinion that its frequent capture would seem to be only a proof of its abun- 

 dance in all t ropieal seas and of the slowness of its movements, which prevent it from going 

 out of the. dredge or net. He believes that although ii and A rgyropelecus are pelagic fishes 

 which live in shoals, it is possible that they may descend to or beyond the hundred-fathom 

 line during the daytime. Why during the daytime only is hard to understand, and it 

 seems to us perhaps judicious to admit that we do not know the conditions of its distribu- 

 tion as regards depth, and to wait for further information before forming any opinion. Dr. 

 Giinther has studied all of the Challenger's specimens carefully and has arranged them in 

 groups with reference to the form of the body. 



The numerous specimens collected by the Challenger differ not inconsiderably in the 

 shape of the body, which, in some specimens, is much more oblique than in others; in the 

 width of the upper surface of the head and neck, and, finally, in the size of the eye, which in a 

 specimen 50 millimeters long is 8 millimeters wide, and in another specimen of the same 



