110 DR. RICHARDSON'S DESCRIPTION OF AUSTRALIAN FISH. 



ring encircling the anterior part of the body contains eighty scales, of which fifteen on 

 each side are above the lateral line, and twenty-four below. 



The head, when the mouth is closed, has a conical profile, with its upper line slightly 

 concave, the lower one rather convex, and the under jaw sloping upwards. Its length, 

 measured to the tip of the gill-cover, is comprised four times in the total length of the 

 fish, caudal included; its transverse diameter increases from the snout to the nape, 

 where it equals that of the body at the pectorals ; between the eyes it is flatly rounded, 

 but on the nape it rises into an acute edge ; and it thins off gradually from beneath 

 the eye to the slender isthmus of the gill-openings. The perfectly round and rather 

 small eye is situated near the upper profile, and at an equal distance from the tip of 

 the snout and gill-opening ; its diameter is contained thrice and one-half in the 

 length of the head, and fully thrice in its height at the orbit. The distance between 

 the orbits rather exceeds the width of the eye. The nostrils are about one-third 

 nearer to the eye tlian to the tip of the snout ; the posterior opening is small and 

 round, the anterior one larger, oblong, and having its hind margin raised. The first 

 suborbitar bone, situated directly before the eye, is rather large, and has a rhomboidal 

 form, its posterior edge being a little shorter than the others : its surface is smooth, 

 nacry, and scaleless, with two or three smooth branching tubes not showing until the 

 epidermis dries ; none of its margins are toothed, though the under one is slightly un- 

 dulated. A narrow edging of smooth skin surrounds the orbit, and a smooth space 

 extends from it over the first suborbitar to the snout. A second and third suborbitar, 

 thin and narrow, are concealed by the scaleless integument. 



The limbs of the preoperculum meet at a right angle, the corner being broadly 

 rounded off. When the integument is scraped off, its perfectly even and nearly mem- 

 branous margin is discovered to be supported by a series of very slender short ridges 

 inclining upwards, but too minute to be distinctly seen without the aid of a lens '. 

 The anterior side of the operculum is the longest, the inferior one is next in length and 

 is convex, the posterior one is slightly concave with rounded corners, and the upper 

 one is the shortest of the four. The suboperculum is narrow and tapers posteriorly, its 

 membranous tip projecting a little beyond the operculum. The interoperculum is broad 

 with an evenly convex lower edge. The cheeks and operculum are covered with scales 

 considerably smaller than those of the body ; the scales of the preoperculum, suboper- 

 culum, and interoperculum are still smaller, those of the latter being very minute as 

 they approach its under edge, near which they altogether disappear. The scales of the 

 upper part of the head terminate at the nostrils by a rounded outline. The narrow 

 membranous edging of the gill-cover, the bones of the humeral chain, and the axilla of 

 the pectoral fin are smooth and scaleless ; but the base of the pectoral anteriorly is 

 scaly. There are no peculiar supra-scapular scales. 



' The left preoperculum has an obtuse notch where the sinuation usually occurs in Diacope ; but this appears 

 to be accidental, as the right preoperculum is quite entire, and there is no projecting knob of the suboperculum. 



