FISH. 3 
one-fourth of the entire length. Depth at the nape rather less than one-seventh of the same. 
Eyes relatively a little larger than in A. cataphractus ; their diameter one-fourth the length of the 
head ; placed high in the cheeks, and distant one diameter from the end of the snout. Upper 
part of the orbit elevated into an osseous ridge on each side of the crown of the head, with a 
spine at its anterior angle, and the ridge itself terminating in a sharp, rather stronger, spine at 
the posterior angle ; both spines directed backwards. Space between the eyes concave, equal- 
ling in breadth not quite one diameter of the eye, with two longitudinal sharp ridges running 
respectively parallel to the ridges of the orbits, but not nearly so much elevated as these last ; 
these ridges terminate posteriorly at a groove, which runs transversely behind the eyes, sepa- 
rating the vertex from the occiput. The snout presents the same four spines, which are to be 
seen in the A. cataphractus, but it does not project beyond the mouth, The lower margin of 
the suborbital presents a somewhat irregular ridge formed by a series of bluntish tubercles, the 
last of which terminates in a very minute spine directed backwards. Limb of the preopercle 
with three diverging smooth ridges, dilating at their extremities into three flattened blunt points, 
which project a little beyond the membrane, but can scarcely be called spines. Opercle with 
one ridge not so strongly marked as those of the preopercle, and not terminating in any distinct 
point, nor even reaching quite to the edge of the membrane. Jaws nearly equal; but the 
upper one a very little the longest ; each with a narrow band of minute velutine teeth: a distinct 
chevron of similar teeth on the front of the vomer, and a short imperfect row on each palatine. 
Tongue smooth. Gill opening large: the branchial membrane not notched, but passing trans- 
versely over the isthmus, to the edge of which it is nevertheless attached on each side. Chin 
clothed with short fleshy cirri; also a few on the lower jaw and branchial membrane ; but they 
are much shorter, and less conspicuous than in the A. cataphractus, especially on the branchial 
membrane, where they are very sparingly scattered. The occiput presents the four usual ridges 
formed of granulated tubercles; and between the innermost pair there is also a much less 
conspicuous, but slightly raised line running longitudinally down the middle : the two innermost 
of the above ridges are nearly in a line respectively with the two ridges of the orbit, behind 
which they commence, and they would pass on to unite with the two dorsal carine were they 
not separated from the latter by a deep transverse depression at the nape: the two outermost of 
the occipital ridges commence behind the eyes themselves, and terminate at the suprascapulars, 
each in a sharp point directed backwards, but not prolonged imtoa spine. The carinated scales 
which arm the body of this species, are more sharply serrated than those of the A. cataphractus, 
the keels terminating behind in hooked points; and the elevated lines which form the striz on 
each side of the keel are fewer in number and more raised. The ridges which they form are 
also more marked, and the second ridge on each side commences immediately behind the angle 
of the opercle, instead of opposite the vent as in that species ; so that the whole body is perfectly 
octagonal from the gills to the termination of the dorsal and anal fins :* at that point, the two 
dorsal ridges and the two ventral unite respectively to form one, or rather approximate so closely 
as to form but one in appearance; for, if closely examined, there will still be found two parallel 
rows of serratures. In each of the two uppermost or dorsal ridges, there are twenty-seven 
scales, reckoning from the hollow at the nape to the point where the ridges unite. In the 
second ridge (which extends, as before observed, from the gills to the caudal) there are thirty- 
* In the A. cataphractus, the body is hexagonal from the gills to a little beyond the vent; octagonal from this 
last point to the termination of the dorsal and anal fins ; then hexagonal again to the end of the tail. 
