FISHES—TRACHINIDAE—HETEROSTICHUS ROSTRATUS. 
37 
may be observed upon the anterior part of the vomer and the palatine bones, transverse and 
triangular, with the summit directed forwards on the former, longitudinal and oblong on the 
latter. A very narrow space separates the palatine patches from the vomerine one. On the 
dentaries, or lower jaw, there is one row of conical teeth, altogether similar in shape to those on 
the upper jaw, or premaxillaries, but are somewhat larger. The eye is of moderate develop¬ 
ment, sub-eliptical in shape ; its horizontal diameter is contained seven times in the length of 
the side of the head, and about twice anteriorly to the orbit. The various pieces constituting 
the opercular apparatus are perfectly smooth, and unprovided with either spines or serratures 
upon their posterior edges. The branchiostegal rays, six on either side, are very much devel¬ 
oped ; the branchiostegal membrane being torn off in the specimen before us, we are at a loss 
to know whether there was an isthmus, or whether the branchial aperture from either side met 
under the throat. At any rate, if an isthmus was present, it could not have been very wide. 
We are inclined, however, to think that the apertures were continuous. The cheeks and the 
upper portion of the opercle are covered with very small scales. 
Most of the dorsal region is occupied by a fin, spinous in structure for the four-fifths of its 
length ; a vertical line drawn from its origin would intersect the opercle through about'its 
middle. The anterior seven rays are situated along the declivity of the nape ; the first is the 
highest of all, and the seventh the smallest, giving to that portion of the fin a sub-triangular 
shape. The rest of the spinous portion, composed of thirty rays, maintains a uniform height 
throughout, and is less elevated than the soft portion. The latter, composed of thirteen or four¬ 
teen articulated but undivided rays, is convex upon its upper margin. The posterior rays, 
when bent backwards, do not quite reach the base of the caudal fin. The caudal fin consti¬ 
tutes the ninth of the total length ; its posterior margin is concave, and its lobes are rounded. 
The rays composing it are simple, or else not bifurcated like those of the dorsal fin. The anal 
is quite long, and deeper than the dorsal. Its base extends somewhat more posteriorly than that 
of the latter, and its posterior rays, when bent backwards, nearly approximate the base of the 
caudal. The anterior two rays are spinous, and shorter than the rest, which remain simple or 
undivided, as in the caudal and dorsal. The portion of that fin placed opposite the soft rays of 
the dorsal is a little deeper than the remaining portion. The base of the anal fin is somewhat 
less than the half of the entire length of the fish. The insertion of the ventrals is situated much 
in advance of the insertion of the pectorals, immediately under the throat. They are long and 
slender, composed of four undivided rays, the external of which in a rather rudimentary state. 
The insertion of the pectorals is placed in advance of a vertical line, which would be drawn from 
the seventh dorsal spine. They are composed of thirteen undivided rays. 
Br. YI: YI; D XXXVII, 13 ; A II, 34; C4, 1,5,4, 1,3; YI,3; P 13. 
The scales are exceedingly small, unimbricated, and but very imperfectly arranged into series. 
They are a little longer than deep, anteriorly almost straight, laterally rounded, and convex 
posteriorly. Radiating grooves run in all directions from the centre to the periphery. The 
lateral line is composed of a series of very conspicuous tubes : starting from the upper and 
posterior angle of the opercle, it forms an undulated arch above the pectoral fins, reaching 
the middle line of the flanks opposite the origin of the anal, hence straightway to the base of 
the caudal. Under the abdomen the scales are minute, almost imperceptible. It has already 
been remarked that the cheeks and the upper portion of the opercle were covered with minute 
scales. We find the latter extending over the rays of the caudal to a considerable extent; also 
