Umbrina arenata, _Cuv. et Val._ Hist. des Poiss. tom. v. p. 141.
FORM.—Rather elongated, with the back very little arched; the greatest
depth contained about five times and a quarter in the entire length.
Length of the head about equal to the depth of the body. Profile
falling very gradually, and nearly in a straight line, in front of
the dorsal. Snout very much projecting; the margin at bottom, above
the upper jaw, divided into four lobes which are cut square at their
extremities. Round the end of the snout, and immediately above the
lobes, is a double row of pores, the lower ones large. Also four
pores beneath the symphysis of the lower jaw. Barbule at the chin
scarcely exceeding a line or a line and a half in length. A band of
velutine teeth in each jaw, with an outer row in card; these last
moderately strong, sharp, and rather wide apart, not above fourteen
or sixteen in the row. Preopercle very obsoletely denticulated.
Opercle with two flat points not much developed.
First dorsal triangular; the first spine very small; the second, third
and fourth elevated rather in a point, the third equalling
two-thirds of the depth of the body or more. Second dorsal nearly
twice the length of the first. Anal commencing opposite the sixth
soft ray of that fin, short, and terminating considerably before it;
the anal spine weak, and very little more than half the length of
the soft rays. Caudal with the posterior margin sinuous, the upper
part being slightly crescent-shaped, the lower portion rounded, and
broader than the upper. Pectorals a very little shorter than the
head. Ventrals attached a little behind the pectorals, and not
passing beyond them. In the axilla of the pectorals is a small
triangular membranous lamina: there is also a narrow pointed one in
the axilla of the ventrals covered with scales. The scales on the
body are thin, rather small, somewhat rhomboidal, with their free
margins ciliated, and with a fan of twelve striæ behind.
B. 7; D. 10—1/25; A. 1/8; C. 17; P. 21; V. 1/5.
Length 9 inches 6 lines.
COLOUR.—“Body mottled with silver and green: dorsal and caudal fins
lead-colour.”—D. _In spirits_, the colour appears dusky brown, with
darker mottlings and silvery reflections; paler beneath. The fins
are dusky, but the basal half of the dorsal is darker than the
upper. The pectorals are darker than the other fins, especially the
inside; on the left pectoral, the dark colour is restricted to three
broad transverse fasciæ. There are also on the pectorals and anal,
and on most of the scales on the body, small blackish dots, as
mentioned in the ‘Histoire des Poissons.’
_A second specimen_, smaller than the above, has the back rather more
arched, the greatest depth being only five times in the length. The
outer row of teeth in the upper jaw is not quite so conspicuous, the
teeth being smaller and closer-set, and consequently more numerous.
The soft dorsal and anal have fewer rays.
D. 10–1/22; A. 1/7; &c.
Length 7 inches 3 lines.
In all other respects similar to the specimen first described.
Habitat, Bahia Blanca, and Maldonado.
As Cuvier and Valenciennes have mentioned individuals of this species,
which varied in the number of rays in the soft dorsal from twenty-two to
twenty-four, I cannot but consider the two above described as
specifically the same, though in the first these rays amount to as many
as twenty-five. This, which is the larger specimen, was taken by Mr.
Darwin at Bahia Blanca, where it is said to have been common. The other
was obtained at Maldonado.