Gerres Oyena, _Cuv. et Val._ Hist. des Poiss. tom. vi. p. 355.
Smaris Oyena, _Rüppell_, Atlas zu der Reise im Nörd. Afr. Zoologie; p.
11. tab. 3. fig. 2.
FORM.—Greatest depth contained rather more than three and a half times
in the entire length: the dorsal curve very regular. Profile above
the eyes a little concave. Length of the head exceeding its depth.
Maxillary as in the species last described. Suborbital with its
lower margin distinctly but not very deeply notched; not
denticulated. Diameter of the eye less than one-third the length of
the head. Posterior orifice of the nostrils twice the size of the
anterior one. No denticulations on any part of the head or
gill-cover. A narrow band of velutine teeth in each jaw, of about
the same length and degree of fineness above and below; but none on
the palate or tongue.
The dorsal commences in an exact vertical line with the insertion of
the ventrals: the anterior spines are a little arcuate; the first,
as in the other species of this genus, is extremely short; the
second and third in this specimen are broken at their extremities so
that their exact length cannot be ascertained, but the portion of
the second remaining (and of this spine apparently only a very small
piece is gone) nearly equals half the depth of the body; length of
the fourth spine which is perfect not quite equalling two-fifths of
the depth; fifth, sixth, and seventh spines gradually decreasing;
eighth and ninth scarcely shorter than the seventh: the second spine
is much compressed, and though obviously stronger than any of those
which follow, not nearly so stout as in many other species; its
breadth is not more than one-twelfth of its length. Anal commencing
in a line with the fourth soft ray of the dorsal; the second spine
compressed similarly to the second dorsal spine, and of about the
same degree of stoutness, but its length one-third less, being just
equal to one-third the depth of the body; the third spine scarcely
shorter than the second, but much slenderer; the soft rays gradually
decreasing from the first, which is a little shorter than the third
spine, to the last but one, the last itself slightly prolonged to
form a point backwards. Caudal forked nearly to its base; the lobes
much elongated; the upper one, which is a trifle longer than the
lower, contained rather more than three times and a half in the
entire length. Pectorals narrow and pointed, a little shorter than
the head, and contained not quite four times and a half in the
entire length; fifth and sixth rays longest. Ventrals attached a
little behind the pectorals, and not much more than half their
length; the spine about three-fourths the length of the soft rays,
and scarcely stouter than the third spine in the anal: the axillary
elongated scale three-fourths the length of the spine. The scales on
the body of this species are not materially different from those of
the _G. Plumieri_ described in the “Histoire des Poissons.”
B. 6; D. 9/10; A. 3/7; C. 17, &c.; P. 16; V. 1/5.
Length 7 inches.
COLOUR.—“White, silvery.”—D. The fins are yellowish; the membranes
here and there dotted with black: the lobes of the caudal are
bordered internally with dusky. I see no trace of the interrupted
longitudinal bands spoken of by Cuvier and Valenciennes, neither is
there any allusion to them in Mr. Darwin’s notes taken from the
recent fish.
Habitat, Keeling Island, Indian Ocean.
I do not feel confident as to this species being, any more than the
last, identical with that to which I have referred it. It requires an
inspection of a large number of specimens in order to ascertain the true
value of characters. The present one agrees with what is stated of the
_G. Oyena_ by Cuvier and Valenciennes, excepting that the second anal
spine, which they represent as shorter than the second dorsal spine by
one-half, is here shorter by one-third only: also, as mentioned above,
there is no appearance of any longitudinal bands. There is no other
species in the “Histoire des Poissons,” to which it approaches more
closely. But comparing it with Rüppell’s figure, if this last be
scrupulously exact, there are a few other differences besides those
already alluded to. Thus the first anal spine in Mr. Darwin’s specimen
appears shorter in relation to the second, and this last stouter as well
as longer. Also the soft rays of this fin gradually decrease, giving a
sloping direction to the margin, whereas in Rüppell’s figure, all the
rays are nearly of the same length, and made equal to the second and
third spines. The caudal lobes, likewise, appear longer in Mr. Darwin’s
specimen. It must be left for others to determine whether these
discrepancies are indicative of a specific difference or not. As regards
the geographic range of the _G. Oyena_, I know not that there is any
thing in this respect to render its identity with the species here
described improbable. It inhabits the Red Sea; and is also said to be
common at the Mauritius;—whence it may very possibly extend as far
eastward as the Keeling Islands, where Mr. Darwin’s specimen was
obtained.
The _Sparus erythrurus_ of Bloch (pl. 261) is so extremely unlike the
present species both in form and colours, that, except on the authority
of MM. Cuvier and Valenciennes, who state that they had seen Bloch’s
original specimen, no one could have suspected that the figure had been
intended for it.