FIG. 89.—Lizard-fish, _Synodus fætens_ L. Charleston, S. C. ] =The Lizard-fishes.=—The _Synodontidæ_, or lizard-fishes, have lizard-like heads with very large mouth. The head is scaly, a character rare among the soft-rayed fishes. The slender maxillary is grown fast to the premaxillary, and the color is not black. Most of the species are shore-fishes and some are brightly colored. _Synodus fætens_ is the common lizard-fish, or galliwasp, of our Atlantic coast. _Synodus varius_ of the Pacific is brightly colored, olive-green and orange-red types of coloration existing at different depths. Most of the species lie close to the bottom and are mottled gray like coral sand. A few occur in oceanic depths. The "Bombay duck" of the fishermen of India is a species of _Harpodon_, _H. nehereus_, with large mouth and arrow-shaped teeth. The dried fish is used as a relish. The _Benthosauridæ_ are deep-sea fishes of similar type, but with distinct maxillaries. The _Bathypteroidæ_, of the deep seas, resemble _Aulopus_, but have the upper and lower pectoral rays filiform, developed as organs of touch in the depths in which the small eyes become practically useless. =Ipnopidæ.=—In the _Ipnopidæ_ the head is depressed above and the two eyes are flattened and widened so as to occupy most of its upper surface. These structures were at first supposed to be luminous organs, but Professor Moseley has shown them to be eyes. "They show a flattened cornea extending along the median line of the snout, with a large retina composed of peculiar rods which form a complicated apparatus destined undoubtedly to produce an image and to receive especial luminous rays." The single species, _Ipnops murrayi_, is black in color and found at the depth of 2½ miles in various seas. [Illustration: FIG. 90.—_Ipnops murrayi_ Günther. ] The existence of well-developed eyes among fishes destined to live in the dark abysses of the ocean seems at first contradictory, but we must remember that these singular forms are descendants of immigrants from the shore and from the surface. "In some cases the eyes have not been specially modified, but in others there have been modifications of a luminous mucous membrane leading on the one hand to phosphorescent organs more or less specialized, or on the other to such remarkable structures as the eyes of _Ipnops_, intermediate between true eyes and phosphorescent plates. In fishes which cannot see, and which retain for their guidance only the general sensibility of the integuments and the lateral line, these parts soon acquire a very great delicacy. The same is the case with tactile organs (as in _Bathypterois_ and _Benthosaurus_), and experiments show that barbels may become organs of touch adapted to aquatic life, sensitive to the faintest movements or the slightest displacement, with power to give the blinded fishes full cognizance of the medium in which they live."