A second specimen is only three inches and a qnavter in leng th ; but differs
in no respect from the above, except in having one soft ray less in the anal fin.
H abitat, River Matavai, Tahiti.
Several of the species in this genus are extremely similar as well in form as
in colours. Possibly that which I have here characterized as new may not be
distinct from the D . malo of Valenciennes, which comes from the same country ;
hut the description in the “ Histoire des Poissons” is so brief, that it is hardly
possible to determine this point with certainty. It has, however, two, and one
specimen three, soft rays less in the anal fin. It is also closely allied to the
D . margiuatiis, from which it hardly differs, excepting in having the denticulations
of the preopercle rather stronger, and the tenth dorsal spine shorter in relation
to the soft rays which follow. The D. marginatus, however, comes from
Java. The species here described was found by Mr. Darwin in Tahiti, in the
river of Matavai.
H e l o t e s o c t o l in e a t u s . Jen.
H . corpore lineis longitudinalibus nigricantihus octo ; pinnis dorsali, anali, caudali-
(jue, maculis fuscis; vertice striis elevatis duobus subparallelis; preoperculo distinclh
denticulato, et ad marginem limbi internum subcristato ; operculo mucronibus duo-
hus, superiore minimo; squamis ubique Icevissiinis.
B. 6; D. 12.9; A. 3,7; C. 17, & c.;P . 15; V. 1,5.
L o n g . u n c . 9. lin . 9.
F o rm .— Body oblong. G reatest depth exactly four and a half times in the entire length. Length
of the head rather less than the depth of the body. Snout short and obtuse. Jaw s exactly
e q u a l: each with a broadish band of velutine teeth, which are all, apparently even the most
minute, three-pointed, although this character is not very obvious except in the outer row, which
are longer than the others. N o vomerine teeth appear externally, but they may be felt through
the skin of the palate, and on dissecting this off, there is brought to view a small hard disk
rough with minute asperities. Mouth very little cleft, the commissure not extending more
than h alf way between the end of the snout and the anterior margin of the orbit. Eyes rather
large ; their diameter one-fourth the length of the head. Maxillary, when the mouth is closed,
concealed in part beneatli the suborbital, the lower margin of which is somewhat sinuous and
obscurely denticulated, the denticulations being concealed by the membrane and more easily
felt than seen. The denticulations on the preopercle very manifest. The principal spine on
the opercle slender and very sharp, not exactly straight, but slightly curved, the convexity of
the bend being downwards; above is a second spine, but very small and easily overlooked.
The crown of the head has two nearly parallel elevated lines, which take their origin between
the nostrils, and term inate at the occiput, but do not meet as in the H . sexlineatus; * a third
line commences tl)ere exactly between them, and runs singly in a backward direction down the
middle of the nape ; this last is scarcely more than half the length o f the two former. The
cheeks and pieces of the gill-cover are scaly; but not the cranium, snout, jaw s, or limb of the
preopercle, which last is margined internally by a slightly elevated ridge. The scales on the
body are thin and small, and without any trace of denticulations on their free edges, even under
a magnifier, and the body of the fish is quite smooth to the touch rubbed either way. Lateral
line as in I I . sexlineatus. Dorsal also nearly similar, but more deeply notched, the membrane
beyond the eleventh spine falling nearly to the base of the twelfth, which precedes the soft
portion : sixth spine longest, equalling very nearly, but not quite, h alf the d ep th ; the eleventh
equals the second ; the twelfth is about one-third longer than the eleventh, but is itself scarcely
lialf the first soft ray. The anal has tln-ee soft rays less than the H . sexlineatus. and there are
apparently but two spines, the first being (at least in this specimen, where, however, there may
have been a portion broken off) quite short and rudimentary ; the second and third spines are
both slender, the former being rather more than half the length of the latter, and this last
rather more than half the first soft ray. All the fins take their origin as in I I . sexlineatxis.
The pectorals are about two-thirds the length of the head. The ventrals, which are very near
together, are longer than the pectorals, but do not equal the h ea d : they have no elongated
scale between them, or in their axill®.
C o l o u r .— For the most part similar to that of the I I . sexlineatus; but the longitudinal dark lines
are more numerous, amounting to eight, with faint traces of a ninth: the additional ones are on
the upper h alf of the sides, or above the lateral line, there being four (instead of two) above
that one which passes through the ey es; the sixth extends the whole length o f the fish from
the end o f the maxillary to the base o f the caud al; the seventh passes immediately below the
pectoral, and terminates in advance of it, without quite reaching to the edge o f the gill-cover;
the eighth is exactly equi-distant from the pectoral and v en tral; this last is a very narrow pale
line, but the others, with the exception of the first two, are broader and well marked. The
soft portion of the dorsal, as well as the anal and caudal are spotted; the spots on this last
unite to form transverse fasci® ; those on the anal are not very well-defined. The pectorals and
ventrals are without spots, and pale.
Habitat, S. W. coast of Australia.
This species was procured in K ing George’s Sound, New Holland. It closely
approaches tlie II. sexlineahis of Cuvier and Valenciennes, the only species of the
genus hitherto described, and obtained in the same seas by MM.Q aoy and G aimard.
I have little hesitation, however, in pronouncing it to be distinct. In dependently
of the additional longitudinal lines on the body, and the spots on the
fins, which, it is expressly stated by the above authors, are not present in the
H . se.dineaius, it is distinguished by the stri<^ on the crown not meeting behind,
the dorsal being rather more deeply notched, and the fin-ray formula different.
* Or at least as represented in the figure in the Histoire des Poissons, tom. iii. pi. 5G.