FISH. 



31 



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. cat ap fir actus ; 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. catapfir actus, 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. catapfir actus, 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 carinas 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 into a spine. The carinated scales 

 which arm the body of this species, are more sharply serrated than those of the A. catapfir actus, 

 the keels terminating behind in hooked points ; and the elevated lines which form the stria? 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. 



