DR. RICHARDSON'S DESCRIPTION OF AUSTRALIAN FISH. 161 



surface into triangular areas are conspicuous enough. There is always a smooth mem- 

 branous line connecting the angle of the mouth with the lower end of the vertical bran- 

 chial slit ; also an irregular membranous space at the upper end of that slit, with some 

 narrow stripes branching between the scales to the posterior border of the orbit, and 

 admitting of a slight degree of motion in these parts. The cuirass terminates posteri- 

 orly on each side by an undulated line, which seems to vary in form in different species, 

 and even in individuals of the same species. In our oldest example of auritus it com- 

 mences at the anterior end of the dorsal, runs parallel to that fin to its termination, 

 whence it descends in a shallow concave curve to the anal, and running forwards to the 

 anus meets there with the corresponding limit of the cuirass of the opposite side. The 

 space behind is thus made to include the three vertical fins and is filled up with mem- 

 brane, but is more or less protected by detached plates, which vary with the species. 

 In auritus a saddle-shaped cluster of small plates bestrides the tail closely behind the 

 dorsal, a small heart-shaped one lies beneath near the anus, and the base of the caudal 

 is armed with a ring of plates, which is narrowest on the sides. In the smallest speci- 

 mens which we have seen of this species, each plate has a small rough cauliflower-like 

 central wart, from whence elevated ridges radiate to the angles and inclose depressed 

 areas. The abdominal plates show an elevated hexagonal bounding line. In older ex- 

 amples, among which is included Shaw's specimen, the radiating lines, though still 

 conspicuous, are more distinctly perceived to be composed of obtuse conical grains, 

 and the central grain, though continuing to be larger than the others, has lost its clus- 

 tered form: the areas are also less depressed. In our largest individual, which is six 

 inches and a half long and three and a half high, the grains are all so nearly equal in 

 size and so equally distributed, and the areas so nearly even, that it is only on a few 

 plates beliind the pectoral that the radiation is readily perceptible, the whole surface 

 being equally granular. 



Tlie profile of Ostracion auritus (excluding the tail) is sub-orbicular, the muzzle pro- 

 jecting conically before, the eye standing a little out of the round. The orbit is mo- 

 derately large, round, and forms a gibbosity in the profile, which from thence to the 

 mouth is slightly convex. From the under lip for a short distance backwards the under 

 outline is concave, but the projecting obtuse abdominal keel, which begins before the 

 line of the eye, is curved in an equal degree with the back. The back is narrower, and 

 the keel of the belly less distinctly pronounced in the younger specimens. The eye is 

 about twice its own diameter behind the tip of the upper hp, and about one diameter 

 above the naked stripe which runs horizontally backwards from the corner of the mouth. 

 Three rows of scales lie above this space on the cheek. The lips are tumid, naked, and 

 plaited within ; the orifice of the mouth is small, and there are five narrow, chisel- 

 shaped umber-brown teeth on each intermaxillary, and eight on the lower jaw. In the 

 young fish the teeth are fewer and further apart. There is a transverse velum in the 

 upper and under jaw. 



