TRACHICHTHYS niETIOSUS. 59 



The lower jaw is furnished at the tip with a prominent hard tubercle, and 

 so projects a little beyond the upper. Both are roughened round the edges with 

 narrow bands of fine, small, brush-like teeth, narrowest in the upper jaw : the 

 vomer, like the ethmoid, is perfectly unarmed and smooth ; but the palatines are 

 furnished with a narrow, but distinct band of minute teeth. The gullet is rough : 

 the tongue quite smooth, distinct, large, thick, blunt, free ; and, like the whole in- 

 side of the mouth and gullet, black. 



The eye, for at least two thirds of its circumference, proceeding from its fore-cor- 

 ner underneath, is surrounded by a series of five or six flattened, winged or 

 dilated, crest-like ribs or ridges, radiating from the edges of the orbit like the 

 spokes of a wheel. They are of variable length, but all of equal height, appearing 

 just as if they had been ground down to the same level; and dividing the suborbi- 

 tary region into cellular compartments. 



The branchial opening is large and wide ; its membrane is supported by eight 

 distinct rays, which are finely rough or serrulate. At its lower angle is a prominent 

 flat tooth, formed by the termination of the ends or branches of the lower jaw, 

 and in a line below the ends of the maxillaries. 



The opercle is small and narrow, twice as high as broad, with a short, trans- 

 verse, serrate keel or ridge towards the top, assuredly not ending in a spine, but in 

 a mere point or angle. From the same point from which originates this ridge, 

 there also radiates a number of strong, oblique, descending, scabrous ribs or striae, 

 roughening the whole. The edge is sinuous, and minutely seiTulate. 



The subopercle is distinct, and large comparatively with the opercle, form- 

 ing below the keel or ridge of the latter the whole hinder edge of the branchial 

 opening. Its edge descends obliquely, rapidly, from just above the pectoral fins, 

 forming a sinus just before their base. It is faintly striated towards its upper 

 broader part or edge ; the striae radiating or diverging upwards from a point below. 

 Its whole edge is membranaceous, thin, and perfectly entire. 



The interopercle forms a convex quadrant of a circle, joining on to the subopercle, 

 on a level with the base of the pectoral fins, and reaching to the prominent tooth 

 or angle which terminates the branches of the lower jaw. It is remarkably 

 broad and short ; but in great part concealed by the overlaying spine and lower 

 angle of the preopercle, leaving exposed only a narrow border, which is striated 

 transversely, having the edge minutely, feebly, and irregularly denticulate. I 

 find no trace of its being " singulierement echancre dans son milieu," Cuv. and 

 Val. : but this expression has arisen, probably, from not distinguishing it from the 

 subopercle. Considered as forming one piece with that bone, there is indeed a 

 remarkable sinus " dans son milieu :" but this is formed by the contraction of the 

 subopercle and interopercle at their junction, close before the base of the pectoral 

 fin. 



The preopercle terminates below in a strong, conspicuous, flattened, horizon- 

 tal spine ; the lower edge of which is straight, and finely serrulate. Its border is 

 nearly vertical and straight, formed by two parallel raised ribs or ridges, like 

 Apogon; of which the hinder, which is its true edge, is minutely sen'ulate towards 

 the bottom. This border is divided equally into four oblong cells, by as many 

 transverse dissepiments ; the two middle ones of which appear like continua- 

 tions of two of the hinder suborbital bony ridges, but are spurious or merely 

 membranous : the two extreme ones are true bony partitions. 



The whole head, and the opercles, lower jaw, and maxillaries, are completely 

 free from scales, or naked, except a small and narrow, oblong, inconspicuous patch 

 vmder the cheeks, just behind the dilated ends of the maxillaries. 



The whole structure of the head is highly curious ; being excavated, as it were, 

 into cellular compartments, separated by rough bony crests or ridges, radiating 



