_P. corpore parum elongato, altitudine quintam partem longitudinis
æquante: galeâ lævi, inconspicuâ, processu interparietali haud
clypeum parvum prædorsalem attingente: poris paucis buccalibus
amplis, serie obliquâ dispositis: maxillis æqualibus: cirris sex;
maxillaribus haud analem attingentibus: lineâ laterali primum
deflexâ, deinde rectâ: pinnis dorsali et anali brevibus; adiposâ
dorsali haud duplo longiore: caudali profundè bifurcâ, lobis
æqualibus: spinâ pectorali margine interno fortiter dentato._
D. 1/7; A. 13 vel 14; C. 17, &c.; P. 1/8; V. 6.
LONG. unc. 3. lin. 6.
FORM.—In some respects resembling the last species, but the body much
less elongated, the depth and thickness remaining the same. The
depth is about one-fifth of the entire length; the head rather more
than one-fifth. The helmet is scarcely so much wrinkled, and the
interparietal process not so long, reaching only half-way to the
buckler, which last is smaller and less obvious. The solution of
continuity of the bones of the cranium appears to extend back in the
form of a narrow fissure nearly to the base of the interparietal
process, but is not very obvious, except between the eyes, where it
opens into a sort of elongated ellipse. There are eight or nine
pores on the top of the head, rather behind the eyes, so arranged as
to form nearly a complete circle. There is also a very conspicuous
row of three or four large oval pores on the cheek, at the anterior
part of the opercle, descending obliquely forwards: other smaller
ones may be seen scattered about different parts of the head. The
jaws are equal: the teeth as in the last species, excepting that a
roughness can be distinctly felt upon the vomer beneath the skin,
though there are no teeth on that part which appear through it. The
maxillary pair of barbules reach to a point midway between the
insertion of the ventrals and the commencement of the anal: of the
submandibular pairs, the exterior do not reach beyond the insertion
of the pectorals; the interior are two-thirds the length of these.
Eyes elliptical, the longitudinal diameter about one-fifth the
length of the head; situate nearer the end of the snout than the
posterior part of the opercle; the interval between them nearly two
diameters. The lateral line slopes downward till opposite the fourth
soft ray of the dorsal, then passes off straight along the middle to
the caudal.
The pectorals are contained about five and a half times in the entire
length. The spine is similar to that of the last species; but the
humeral bone is shorter, and scarcely one-third of the pectoral
itself. The dorsal is similar; and the space between it and the
adipose is the same; but the adipose itself, though of the same
form, is not so long, from the body being less elongated; it is not
more than half as long again as the dorsal. Anal similar, but the
adipose not advancing so much beyond it. Caudal and ventrals
similar; but the former with the lobes equal.
COLOUR.—(_In spirits._) On the whole similar to, but darker than that
of the last species. There is some appearance of a fascia along the
lateral line. The upper part of the dorsal, and also of the anal, is
dusky, but there is no spot on the adipose. Pectorals and ventrals
dusky.
A _second specimen_ differs from the above in no respect, except in
being smaller, measuring two inches and a quarter in length, and in
having one ray more in the anal.
Habitat, Rio de Janeiro?
The number annexed to this species has been lost, but there is reason
for believing that Mr. Darwin took it with the last at Rio de Janeiro. I
cannot identify it with any of those described by Cuvier and
Valenciennes in the “Histoire des Poissons.”—It affords another instance
of the indefiniteness of the character derived from the presence or
absence of vomerine teeth; since a band of such teeth, which are
considered by Valenciennes as absent in this genus, can be distinctly
felt and made obvious by removing the skin of the palate, though they do
not appear externally. This is not the case with the species last
described, to which nevertheless, the present one approaches so closely
in general character, that they never could be widely separated. Except
for the greater elongation of the body in the _P. gracilis_, I should
have been almost inclined to consider them as sexes of the same species.