DR. RICHARDSON'S DESCRIPTION OF AUSTRALIAN FISH. 117 



ofT above the lateral line, it also terminates in an acute ridge. The vent is midway 

 between the snout and tips of the central caudal rays. The head, measured to the gill- 

 opening, forms nearly one-third of the whole length ; when viewed from above, it is 

 Seen to increase gradually in thickness from the very narrow snout to the shoulder, 

 having a transversely convex surface from the nostrils to the nape, and a smooth, acute, 

 mesial ridge between the nape and first dorsal spine. The nostrils consist of two small 

 openings near each other, and close to the orbit. The moderately large eye, situated 

 midway between the tip of the snout and the upper angle of the gill-covering, occupies 

 about one-third of that space. The orbits approach close to the profile of the head, 

 without altering its lines, and the space between them is equal to the diameter of the 

 eye. 



The mouth is small, its gape scarcely extending half way to the eye ; lips tumid ; in- 

 termaxillaries moderately protractile, the labial sliding entirely under the infra-orbitar 

 when the mouth is shut, but exposed for its whole length when the jaws are extended. 

 The teeth, minute and slender, stand in a single row on the intermaxillaries and lower 

 jaw, but they cannot be readily seen without the aid of a microscope. The palate and 

 vomer are toothless, and are lined by a dark-coloured membrane, which is longitudinally 

 plaited towards the gullet, and is crossed at the knob of the vomer by a crescentic 

 velum. The tongue is smooth, and has little liberty. Each limb of the lower jaw is 

 perforated by four pores, and its thin expanding inferior edge can approach its fellow 

 so as to overlap the isthmus of the branchiostegous membrane. The preorbitar is 

 quadrilateral, with the anterior corners rounded. If there be a chain of infra-orbitars 

 under the eye, they are so thin that they cannot be distinguished from the nacry skin. 



The gill-covers, composed of very thin smooth bones, devoid of spines, serratures, 

 ridges, or grooves, are covered like the cheeks and side of the head by a thin nacry 

 skin, in which no scales can be detected. The preoperculum is broad, with a very thin, 

 entire, posterior edge, its corner rounded, and the two limbs diverging at a right angle. 

 Interoperculum also broad and large, forming a shghtly angular corner beneath, at the 

 junction of its curved inferior and posterior margins. Suboperculum having a narrow 

 strap-shaped form, its membranous tip protruding slightly at the apex of the gill-cover. 

 Operculum cut away posteriorly, in a line which is scarcely concave, and leaves no 

 projecting corners ; its membranous edging is narrow. The gill-openings are large. 

 The branchiostegous membrane is narrow, and much concealed under the projecting 

 edge of the interoperculum ; and the rays, three in number, are short. There are no 

 pharyngeal teeth, some minute points only being discernible by the aid of a lens at the 

 junction of the branchial arches beneath. The exterior arch is furnished with a row of 

 moderately long, slender, awl-shaped rakers ; on the other arches there is merely a series 

 of little knobs, each armed with about three diverging hair-Uke teeth. 



Scales. — ^The upper surface of the head is clothed with dehcate small scales, which 

 terminate in a point between the nostrils, the rest of the head being either quite naked 



