PLATE XXIII. fig. 3.
_T. corpore ovali, subelongato, valde compresso; altitudine tertiam
partem longitudinis, caudali exclusâ, æquante: osse maxillari paulo
dilatato, recto: pinnâ dorsali suboblongâ, altâ, pone ventrales
exorienti; anali scabrâ, altitudine retrò gradatim decrescente;
radiis plicis membranaceis nullis: squamis in lineâ laterali
circiter 38, in lineâ inter pinnas ventrales et dorsalem transversâ
12._
D. 1/9; A. 3/22; C. 19, &c.; P. 13; V. 8.
LONG. unc. c. 3. lin. 7.
FORM.—Still more oval and elongated than the last species, the profile
falling in a gentle curve from the dorsal to the end of the snout.
Depth exactly one-third of the length, excluding caudal: head
one-fifth of the entire length, caudal included. Maxillary rather
dilated towards the bottom, and quite straight, not curving
backwards as in both the last species. Teeth rather larger, and more
conspicuous. Nostrils larger. Only twelve scales in the depth, the
lateral line occupying the seventh row from the top: thirty-seven or
thirty-eight in the lateral line. Scales of a rather different form;
the basal margin more sinuous, the free margin not so regularly
curved, the coloured striæ hardly obvious. Dorsal more oblong than
triangular, higher in relation to the depth, of which it equals
two-thirds, commencing at a point anterior to the middle of the
length, excluding caudal. The pectorals reach a little beyond the
ventrals, which are attached a little in advance of the dorsal. The
anal has all the rays longer, and more nearly equal, the posterior
part of the fin not being so much sloped off: there are three spines
at the commencement, the first two minute, the third not quite half
the length of the soft rays: this fin is furthermore distinguished
from that of the two former species by the rays being set with
asperities, which communicate a scabrous harsh feel to the touch,
when the finger is passed along them from the base upwards.
COLOUR.—Not noticed in the recent state. In spirits it appears more
silvery than either of the two last species: the back and upper part
of the sides being brownish. A humeral dusky spot, and the remains
of what was probably a bright silver band along the middle of the
side from the gill to the caudal. At the base of the caudal is a
dusky spot, which is prolonged in a line along the central rays to
the commencement of the fork. The other fins faintly edged with
dusky, but otherwise pale.
Habitat, Rio de Janeiro.
The more oval and elongated form, straight maxillary, and scabrous anal
fin, at once distinguish this species from either of the two last. It
was taken by Mr. Darwin in fresh water, at Rio de Janeiro, in June.