A large family (over 100 known living species), mostly of pelagic and deep-sea Fishes. A great number of fossil types have been described.
Recent genera:
A. Without photophores: Saurus, Saurida, Bathysaurus, Harpodon, Scopelarchus, Aulopus, Odontostomus, Omosudis, Sudis, Paralepis, Bathypterois, Benthosaurus, Chlorophthalmus, Ipnops. B. With photophores: Scopelus, Dasyscopelus, Neoscopelus, Scopelengys, Nannobrachium, Scopelosaurus.
Fossil genera:
A. Cretaceous: Sardinioides, Acrognathus, Leptosomus, Sardinius, Dactylopogon, Nematonotus, Microcoelia, Opisthopteryx, Apateodus, Rhinellus. B. Eocene, Oligocene, and Miocene: Omiodon, Scopeloides, Parascopelus, Anapterus.
Fig. 371.—A, Scopelus crocodilus (after Goode and Bean). B, Bathypterois dubius (after Collett). C, Ipnops murrayi, with dorsal view of head (after Goode and Bean).
The members of this Family vary much in form, and among them are to be found some of the most curious adaptations to bathybial existence. One of the best known is Harpodon nehereus, which, when newly taken, is brilliantly phosphorescent all over the body; in a salted and dry condition it is the "Bombay-duck," a delicacy eaten with curries, and exported in large quantities from the west coast of India. It is not known to occur at any great depth, and is not even restricted to the sea, being very abundant in the rivers and estuaries of Bengal and Burma; whilst an allied species, H. squamosus, is found in the Indian Ocean at depths of 120 to 300 fathoms. In Bathypterois, the eyes are very small; some of the rays of the paired fins being excessively prolonged, acting as tactile organs, and compensating the reduction in the eyes. Sir John Murray has observed about B. longipes: "When taken from the trawl [from 2650 fathoms] they were always dead, and the long pectoral rays were erected like an arch over the head, requiring considerable pressure to make them lie along the side of the body; when erected they resembled Pennatulids like Umbellula." In Ipnops, which resembles in general form the large-eyed Chlorophthalmus gracilis, the upper surface of the broad spatulate snout is occupied by a luminous organ longitudinally divided into two symmetrical halves, and the eyes are absent, unless, as first supposed, this extraordinary organ be a modification of them; but Professor Moseley's examination seems to have proved beyond doubt that it is a special form of phosphorescent organ, the object of which would be to attract other creatures to the wide gape of a Fish which, living in the abysses of the sea and deprived of organs of sight and touch, would have great difficulty in procuring its food. Odontostomus, with a very large eye which can be turned upwards and sidewards, and enormous compressed curved teeth, barbed at the tip and depressible backwards, is one of the few Scopelids in which scales are completely absent.
The numerous species (about 50) of Scopelus and their allies are moderate-sized or small pelagic and deep-sea forms found in nearly all the seas, some coming to the surface at night, whilst others are confined to great depths; they are remarkable for the series of phosphorescent spots (photophores) on the body, and in some species also on the head, where they may form large patches on the snout. The arrangement of these photophores is a very definite one, and it has been used for the division of these Fishes into genera or sub-genera.[[692]] The ventral fins have a more forward position than in most other members of the Family.
Fam. 7. Alepidosauridae.—Characters as in the preceding, but supratemporal simple, attached to the opisthotic, and dorsal fin very long, formed of slender, non-articulated, simple or bifid rays, extending along nearly the whole length of the back, followed by a small adipose fin. The air-bladder is absent and the body scaleless. The skeleton is feebly ossified; the dentition is very powerful, some of the teeth on the palate and mandible being very strongly enlarged. 4 or 5 species are known, from considerable depths in the Atlantic and Pacific Oceans, referable to one genus, Alepidosaurus or Plagyodus. A. ferox, from the Atlantic, reaches a length of 4 feet.