This very singular form is one of the discoveries of the “Challenger;” it is widely distributed over the seas of the Southern Hemisphere, in depths varying from 520 to 2600 fathoms. The elongate pectoral rays are most probably organs of touch. Four species were discovered, the largest specimen being thirteen inches long.
Harpodon.—Body elongate, covered with very thin, diaphanous, deciduous scales. Head thick, with very short snout; its bones are very soft, and the superficial ones are modified into wide muciferous cavities; the lateral canal of the body is also very wide, and a pair of pores corresponds to each scale of the lateral line, one being above, the other below the scale. Cleft of the mouth very wide; intermaxillary very long, styliform, tapering; maxillary absent. Teeth card-like, recurved, unequal in size; the largest are in the lower jaw, and provided with a single barb at the posterior margin of the point. Eye small. Ventral fins long, nine-rayed, inserted below the anterior dorsal rays; dorsal fin in the middle of the length of the body; adipose fin small; anal of moderate length; caudal fin three-lobed, the lateral line being continued along the central lobe. Centre of the vertebræ open in the middle.
Two species only are known of this singular genus; both are evidently inhabitants of considerable depths, and periodically come nearer to the surface. One (H. nehereus) is well known in the East Indies, being of excellent flavour. When newly taken its body is brilliantly phosphorescent. When salted and dry it is known under the names of “Bombay-ducks” or “Bummaloh,” and exported in large quantities from Bombay and the coast of Malabar. The second species (H. microchir) exceeds the other in length, and has been found in the sea off Japan.
Fig. 269.—Scopelus boops.
Scopelus.—Body oblong, more or less compressed, covered with large scales. Series of phosphorescent spots run along the lower side of the body, and a similar glandular substance sometimes occupies the front of the snout and the back of the tail. Cleft of the mouth very wide. Intermaxillary very long, styliform, tapering; maxillary well developed. Teeth villiform. Eye large. Ventrals eight-rayed, inserted immediately in front of or below the anterior dorsal rays. Dorsal fin nearly in the middle of the length of the body; adipose fin small; anal generally long; caudal forked. Branchiostegals from eight to ten.
The fishes of this genus are small, of truly pelagic habits, and distributed over all the temperate and tropical seas; they are so numerous that the surface-net, when used during a night of moderate weather, scarcely ever fails to enclose some specimens. They come to the surface at night only; during the day and in very rough weather they descend to depths where they are safe from sunlight or the agitation of the water. Some species never rise to the surface; indeed, Scopeli have been brought up in the dredge from almost any depth to 2500 fathoms. Thirty species are known. Gymnoscopelus differs from Scopelus in lacking scales.
Ipnops.—Body elongate, sub-cylindrical, covered with large, thin, deciduous scales, and without phosphorescent organs. Head depressed, with broad, long, spatulate snout, the whole upper surface of which is occupied by a most peculiar organ of vision (or luminosity), longitudinally divided in two symmetrical halves. Bones of the head well ossified. Mouth wide, with the lower jaw projecting; maxillary dilated behind. Both jaws with narrow bands of villiform teeth; palate toothless. Pectoral and ventral fins well developed, and, owing to the shortness of the trunk, close together. Dorsal fin at a short distance behind the vent; adipose fin none; anal fin moderately long; caudal subtruncated. Pseudobranchiæ none.
This singular genus, one of the “Challenger” discoveries, is known from four examples, obtained at depths varying between 1600 and 2150 fathoms, off the coast of Brazil, near Tristan d’Acunha and north of Celebes. All belong to one species, I. murrayi. The eye seems to have lost its function of vision and assumed that of producing light. The specimens are from 4 to 5½ inches long.
Paralepis.—Head and body elongate, compressed, covered with deciduous scales. Cleft of the mouth very wide; maxillary developed, closely adherent to the intermaxillary. Teeth in a single series, unequal in size. Eye large. Ventrals small, inserted opposite or nearly opposite the dorsal. Dorsal fin short, on the hinder part of the body; adipose fin small; anal elongate, occupying the end of the tail; caudal emarginate.