_C. supra virescenti-niger, lateribus pallidioribus: dorso modice
arcuato; fronte elevato, rostro summo ante oculos paululum excavato:
limbo preoperculi ports quatuor conspicuis impresso: squamis latis,
marginibus liberis levissime ciliatis: spinis dorsalibus quindecim,
analibus sex: pinnis ventralibus longe acuminatis, ad analem
pertingentibus: pinnâ caudali subæquali._
D. 1–5/10; A. 6/8; C. 16, &c.; P. 14; V. 1/5.
LONG. unc. 5. lin. 9.
FORM.—Oblong-oval, very much compressed; the back moderately elevated,
and more curved than the abdomen. Greatest depth a little behind the
insertion of the pectorals, and contained twice and three quarters
in the entire length: thickness about two-fifths of the depth.
Forehead high: profile falling very obliquely, and slightly hollowed
out in front of the eyes; the upper and under profile meeting at the
mouth at nearly a right angle. Head contained not quite four times
in the entire length; its own length and height nearly equal. Mouth
small, protractile: jaws about equal, the lower one, if anything, a
little the longest: lips not very fleshy. Maxillary rather slender,
retiring almost entirely, when the mouth is closed, beneath the
suborbital, the anterior margin of which is slightly hollowed out,
and somewhat sinuous. Teeth in card in both jaws, forming a narrow
band; the outermost row longer and stronger than the others,
especially the four or six middle ones in front, which are somewhat
conical and slightly hooked. Pharyngean teeth present, but none on
the vomer or palatines. Eyes rather small, their diameter about
one-fifth the length of the head; high in the cheeks, and a little
nearer to the snout than to the posterior margin of the opercle: the
space between broad, equalling nearly two diameters and a half.
Nostrils consisting of a single round orifice half-way between the
eye and the end of the snout. Preopercle with the basal margin
short, and forming a slightly obtuse angle with the ascending one,
the margin of which is entire. Opercle of a triangular form, broad
at top, but narrowing off towards the bottom. Subopercle and
interopercle much developed; their outer margins, taken together,
rounded off nearly in a semicircle. Branchial membrane quite free
all round, unattached to the isthmus, and but slightly emarginate.
Snout, suborbital, jaws, and limb of the preopercle, naked; but the
cheeks and rest of the opercular pieces scaly: the scales on the
subopercle large. Four large pores on the limb of the preopercle,
preceded by three others beneath the lower jaw: similar pores
beneath the eye, and extending partially round it; one on the crown
of the head, and a few smaller ones scattered about the snout; a
large one just above the opercle, and another higher up on each side
of the nape.
[Illustration:
_Fish Pl. 21._
_Scarne Chlorid_
]
Scales on the body large; about twenty-five or twenty-six in a
longitudinal row, and eleven or twelve in the depth; broader than
long, with the free edges very minutely ciliated, the concealed
portions with a fan of thirteen striæ, and the basal margins with
twelve distinct crenatures. Lateral line interrupted; its first
portion at the depth of two and a half rows of scales beneath the
dorsal, and stopping beneath the commencement of the soft part of
that fin; recommencing three rows lower down, exactly in the middle
of the depth, whence it runs straight to the caudal.
Dorsal commencing above the opercle; the spinous portion of nearly
uniform height, and scarcely more than one-fifth of the depth; the
soft portion much higher, and terminating in a sharp point behind.
Anal answering to the posterior half of the dorsal, terminating
opposite to it, and similarly pointed; with six spines, which, as
well as the dorsal spines, are furnished with very conspicuous
filamentous tags. Caudal nearly even. Pectorals rounded, but not
very broad, their length rather more than three-fourths that of the
head; the rays rather slender. Ventrals pointed; the first soft ray
elongated, and reaching to the anal when laid back; the last ray
attached at its base by a membrane to the abdomen. Rows of small
scales between the rays of the caudal at the base of the fin; and a
few small ones along the base of the dorsal and anal, more
particularly on the soft portions.
COLOUR.—“Above, greenish black; the sides paler; slightly
iridescent.”—D.—In spirits it appears of a nearly uniform brown all
over, fins included.
Habitat, Maldonado, Rio Plata.
Mr. Darwin obtained this species at Maldonado, in a lake of fresh water,
said sometimes to be a little brackish. It appears to belong to the
genus _Chromis_ of Cuvier, placed by him amongst the _Labridæ_, but
having evidently very strong affinities to some of the _Sciænidæ_. It
differs essentially from the _C. Brasiliensis_ of Quoy and Gaimard,[32]
in having six anal spines, and being destitute of all markings and
spots. I am not aware that it is described by any author.
1. SCARUS CHLORODON. _Jen._
PLATE XXI.
_S. æruginoso cyaneus, capite et pinnis flavo-vittatis: maxillis
exteriùs lævibus, marginibus crenatis; caninis ad angulos oris
nullis: fronte gradatim proclivi: lineâ laterali tubis parum
ramosis: squamis ubique striato-granulatis: pectoralibus acuminatis,
radiis superioribus arcuatis: caudali radiis externis cæteris
longioribus, acuminatis._
D. 9/10; A. 3/9; C. 13. &c.; P. 15 vel 16; V. 1/5.
LONG. unc. 16.
FORM.—Of an oval form; the greatest depth one-third of the length,
caudal excluded: dorsal and ventral lines equally convex. Head a
little less than the depth of the body, not gibbous in front, but
with the profile falling regularly and gradually from the
commencement of the dorsal. Snout rather pointed. Jaws equal, their
outer surface smooth, but crenated on their cutting edges. No
spinous canines at the corners of the mouth. Eyes rather small,
their diameter not one-fifth the length of the head, situate above
the middle of the cheek, but equidistant from the posterior lobe of
the opercle and the extremity of the snout. Snout in front of the
eyes, and the lips, naked; but the cheeks and opercular pieces
covered with large scales, which form two rows on the cheeks.
Opercle terminating behind in a rounded angle. Scales on the body
very large; eight in the depth, and twenty-one or twenty-two in the
length: the entire exposed portion of each scale scabrous with
granulations, which are partially disposed in lines towards the free
edges. No scales on the vertical fins. The lateral line occupies the
second row of scales from the top, till it reaches a little beyond
the end of the dorsal, where it becomes interrupted, recommencing in
the fourth row, which at this point is the third: tubal pores in
some places ramified, but the ramifications not very distinct.
The dorsal commences above the posterior lobe of the opercle, and is
of nearly uniform height throughout. The length of the rays in the
soft portion, which is slightly higher than the spinous, is not
quite one-third of the depth. The whole length of this fin is half
the entire length. The anal answers to the last half of the
dorsal, and terminates in the same line; the three spines are
slender, and the first very short. Caudal with the central portion
slightly convex, but the three outer rays above and below
prolonged into a point one-third the length of the whole fin; the
lower point a little longer than the upper. Pectorals about
one-fifth of the entire length, pointed, with the upper rays
arcuate. Ventrals immediately beneath them, one-third shorter.
COLOUR.—“Fine verditer blue, with some yellow stripes about the head
and fins.”—D.—The dried skin is nearly of a uniform brown, but the
snout and cheeks are much varied with green: the jaws also are
green. A bright green patch in front of the eye, immediately beneath
which is a pale frænum, probably yellow in the recent state. Dorsal
and anal green: the former shews some trace of a lighter narrow band
running longitudinally below the upper edge of the fin; the latter
exhibits a very distinct fascia running along the middle. Caudal
pale green, with the upper and lower edges of a much deeper tint.
Ventrals in like manner edged with green. Pectorals wholly dusky.
Habitat, Keeling Island, Indian Ocean.
In so extensive a genus as the present, and one in which so much general
similarity prevails amongst the species, the task of determining whether
any particular one has been described before is extremely difficult. I
can only say that the species which I have here ventured to characterize
as new has been carefully compared with the descriptions of all those
noticed in the “Histoire des Poissons,” and though there are several to
which it is nearly allied, there is none to which it can be referred
with certainty. It seems to approach nearest the _S. variegatus_, but
that species is said to have the caudal square, by which I presume is
meant that the upper and under rays are not prolonged into a point, as
is the case in so many species of this genus, and in the one here
described.
This species was taken by Mr. Darwin at the Keeling Islands.