PLATE IX. fig. 2.
FORM.—Oblong-oval; the body much compressed. Greatest depth rather
more than one-third of the entire length: head one-fourth of the
same. Snout short and obtuse; the profile rising very obliquely, and
forming with the dorsal line one continuous curve. The back is
sharp, and appears more elevated than it really is, in consequence
of the dorsal fin being thickly coated with scales, and scarcely
distinguishable from the body. Ventral line less convex than the
dorsal; the edge of the abdomen somewhat carinated between the
ventral and anal fins, but in advance of the former rounded. The
upper and under profile meet at the mouth at a right angle. Mouth
small, and scarcely at all protractile. Jaws equal; each with a
single row of cutting teeth, which are small, though rather larger
below than above, even and closely set, forming a compact series: no
secondary teeth behind: vomer rough with minute velutine teeth. When
the mouth is closed, no portion of the maxillary is concealed by the
suborbital. Eyes round, moderately large, their diameter rather less
than one-third the length of the head, placed high in the cheeks,
and nearer the end of the snout than the posterior angle of the
opercle, the distance from the former being rather less than one
diameter. The nostrils consist of a single minute round aperture,
about half-way between the eye and the anterior margin of the
suborbital. The suborbital has its margin entire as far as the end
of the maxillary, at which point it curves backwards and upwards to
form a narrow band beneath the eye, and the lower margin of this
band is denticulated. The preopercle is likewise denticulated; but
the denticulations, which are principally confined to the ascending
margin, are not very obvious, and more readily felt than seen: the
angle at bottom is rounded, and rather exceeds a right angle; a
vertical from the angle would form a tangent to the posterior edge
of the orbit: the ascending margin is not quite straight, bending
slightly inwards a little below the middle. The opercle terminates
posteriorly in a very obtuse angle, and shows some indication of two
very minute flattened points, which, however, do not project beyond
the membrane: from the lowermost of these points the margin of the
subopercle passes obliquely forwards to form a continuous curve with
that of the interopercle, which is tolerably well developed.
Gill-opening of moderate size: the branchial membrane, which
apparently has only four rays, has a shallow notch in front, and
passes continuously from one side to the other, without being
attached to the isthmus.
The lateral line commences at the upper angle of the opercle, and,
inclining upwards, runs parallel, not to the dorsal line which can
hardly be distinguished, but to the upper edge of the dorsal fin,
its distance from which is contained about three times and a half in
the entire depth; it terminates a little before the termination of
that fin. Cranium, snout, cheeks, pieces of the opercle, the body,
and all the vertical fins, covered with finely ciliated scales;
those on the crown and snout small, but those on the opercle and
body large; the latter arranged in oblique rows; about twenty-seven
in a longitudinal line from the gill to the caudal, and about
fourteen in a vertical one from the dorsal to the ventral line: a
scale taken from the row beneath the lateral line, and about the
middle of the body, is of an oblong form, its breadth exceeding its
length, with the free edge dotted and finely ciliated, the basal
margin rather deeply crenated, the crenations separated by seven
striæ, which are carried on for only a short way, and do not
converge to a fan. The scales on the dorsal and anal fins are small
and closely compacted; those on the former arranged obliquely, but
the line of obliquity is in the opposite direction to what it is on
the body.
The dorsal fin commences in a line with the posterior angle of the
opercle, and occupies a space equalling half the entire length: the
height of the spinous portion is nearly uniform, but slightly
increases backwards; between the tips of the spines, the membrane is
a little jagged: the soft portion is scarcely more than one-third
the spinous in length, but is somewhat higher, terminating upwards
in an acute angle; the longest of the soft rays is about half the
depth of the body, the dorsal fin itself not included. The anal
answers to the soft portion of the dorsal, which it exactly
resembles; it has two spines in front, the first of which is very
short, and scarcely more than one-third the length of the second,
which itself is shorter than the soft rays; the second spine is
stouter than any of the dorsal spines. These two fins terminate in
the same vertical line. The caudal appears to have been square, but
the rays are worn at the tips, so that its exact form cannot be
ascertained; it is coated with scales for four-fifths of its length
from the base. Between the dorsal and the caudal fins is a space
equalling not quite one-third the depth of the body. Pectorals
attached a little behind the opercle, and a little below the middle;
slightly pointed; about the length of the head or rather shorter;
the first ray only half the length of the second; fourth and fifth
longest; all the rays, with the exception of the first two and the
last two or three, branched. Ventrals attached a little further back
than the pectorals; the first soft ray prolonged into a filament
reaching to the commencement of the anal; the spine is about half
the length of the filamentous ray, and about two-thirds that of the
second soft ray. Between these fins is an oval lanceolate scale
about one-third their length; and in their axillæ another elongated
one, narrower and more pointed than the former, and rather exceeding
it in length.
B. 4; D. 12/16; A. 2/12; C. 15, and 4 short; P. 21; V. 1/5.
Length 3 inches.
COLOUR.—Not noticed in the recent state. _In spirits_, the whole fish,
fins included, appears of a uniform dark brown.
Habitat, Porto Praya, Cape Verde Islands.
The only specimen of this new genus which exists in the collection was
taken by Mr. Darwin off Quail Island, in the bay of Porto Praya. It is
small, but probably full-sized, or nearly so; since the greater part of
the species of _Pomacentrus_, to which genus it is so strongly allied,
average about the same dimensions. Possibly some of the generic
characters, which I have given above, may prove hereafter to be merely
specific; but till other species shall have been discovered, their exact
value cannot be ascertained.