_C. corpore crassiusculo, subelongato; altitudine vix quartam partem,
longitudinis æquante, capite quartam superante; maxillâ inferiore
longiori; oculis magnis; suborbitalibus venis nonnullis
subparallelis obscuris notatis; lineâ laterali parum deflexâ, anticè
squamis parvis inermibus, posticè laminis carinatis 35 vel 36 tectâ;
spinâ reclinatâ ante pinnam dorsalem sub cute occultâ; pectoralibus
longis, falcatis, ad initium pinnæ analis prope pertingentibus._
D. 8—1/26; A. 2—1/22; C. 17, &c.; P. 21; V. 1/5.
LONG. unc. 11. lin. 9.
FORM.—Thicker and deeper in the body than the _C. trachurus_. The
greatest depth a little less than one-fourth of the entire length;
the thickness exceeding (but by a very little) half the depth. Head
large; its length a little more than one-fourth of the entire
length; its height or depth, taken in a line forming a tangent to
the posterior part of the orbit, less than its own length by
two-sevenths. Eyes large; their diameter very nearly one-third the
length of the head; partially covered at the sides by two fatty
membranous veils, as in several other species. The ventral line of
the body is rather more curved than the dorsal, and the upper
profile in like manner a little more approaching to rectilineal than
the lower. The lower jaw a little the longer, and ascending to meet
the upper. Maxillary reaching not quite to beneath the middle of the
eye; its extremity truncated in the form of an arc, with the
curvature inwards. In each jaw a single row of very fine, minute,
closely set teeth; two small patches on the anterior extremity of
the vomer, a band on each palatine, and one on the tongue, all
closely shorn velutine. Suborbital, on each side of the extremity of
the snout, marked with several nearly parallel dark-coloured veins.
Preopercle with the angle very much rounded; the limb broad,
slightly striated or veined, and not separated from the cheek by any
salient ridge. The other pieces of the gill-cover taken together are
bounded posteriorly by a sinuous and very irregular margin, the
notch in the bone at the upper part of the opercle being nearly
semicircular, beneath which is an obtuse point, whence the obliquely
descending margin first slopes slightly inwards, then passes
outwards to form another blunt point lower down, then slopes inwards
again. The course taken by the margin of the membrane in some
measure follows that of the bone, but the sinuosities and salient
angles are more rounded. Cheeks and opercle scaly, as well as the
cranium and forehead between the eyes.
The lateral line does not deviate very much from rectilineal. The
deflection, such as it is, may be said to commence in a line with
the termination of the first dorsal, and to end beneath the first
third of the second dorsal. Up to this point, the scales which
cover it are small and round; but they then begin gradually to
enlarge, and to assume a keel terminating posteriorly in a short
spine: these scaly laminæ continue increasing in size till they
arrive beneath the last quarter of the fin, where they are most
developed; none of them, however, are very large, and even here
they do not extend over the whole breadth of this part of the
tail, nor their own breadth exceed one-eighth of the greatest
depth of the body. After passing the dorsal and anal fins, they
rapidly diminish as they approach the caudal. The entire number of
laminæ may be set at thirty-five or thirty-six; but as it is
difficult to fix the exact point where they commence, it will vary
according as the computation is made more or less in advance. The
anterior portion of the lateral line, bend included, is a little
longer than the posterior.
The reclined spine in this species is entirely concealed beneath the
skin. The pectorals are long and falcate, terminating in a sharp
point: their length nearly equals that of the head, or about
one-fourth of the entire length: when laid back, they reach over
the anal finlet, and very nearly to the commencement of the true
anal. The ventrals are attached a little behind the pectorals, and
are only half as long. The other fins are much as in the other
species of this genus. The height of the anterior part of the
first dorsal equals exactly half the depth. The lobes of the
caudal are one-fifth of the entire length.
COLOUR.—Not noticed in the recent state. _In spirits_; silvery on the
abdomen and lower half of the sides, passing above the middle, and
on the back, into pale lead blue, tinged with gray and brownish:
fins pale greyish brown. No conspicuous markings, except the usual
spot on the notch of the opercle, which, however, is small, and
confined entirely to the membrane.
Habitat, Tahiti.
This species belongs to the second section adopted by Cuvier and
Valenciennes in this genus; or that in which the form of the body
resembles that of the _C. trachurus_, but in which the laminæ on the
lateral line only extend over the posterior portion, the anterior being
smooth and simply covered with small scales. But it will not exactly
accord with any of the species described by those authors. It seems to
approach most nearly the _C. Plumieri_; but though the eyes are of
considerable size, they are not quite so large as they are represented
to be in that. There seem, in fact, to be several species characterized
by large eyes. Spix and Agassiz have figured one from America under the
name of _C. macrophthalmus_; and under the same name Ruppell has figured
another from the Red Sea. Both these, however, appear likewise different
from the one here described, at the same time that their different
geographic range renders their identity _à priori_ improbable. The
present one was taken by Mr. Darwin at Tahiti.