Gerres Gula, _Cuv. et Val._ Hist. des Poiss. tom. vi. p. 349.
FORM.—Greatest depth one-fourth of the entire length. Back but little
elevated. Space between the eyes flat, with a fovea in the middle,
which is prolonged in a channel nearly to the extremity of the
snout. Length of the head exceeding its depth by one-fourth, and
contained about three times and three quarters in the entire length.
So much of the maxillary as is visible is of an oval form, its
length being twice its breadth at its posterior extremity.
Suborbital with the lower margin very indistinctly notched, and not
denticulated. Eyes very large, their diameter contained twice and
three quarters in the length of the head. The two orifices of the
nostrils of nearly equal size. No denticulations on any of the
pieces of the gill-cover. A narrow band of very minute velutine
teeth in each jaw, those above hardly visible to the eye, but
sensible to the touch: none on the vomer, palatines, or tongue.
Dorsal with the first spine extremely short; the second has a small
piece broken off at the tip, but appears to have been about the same
length as the third, which last equals two-thirds of the depth of
the body; the fourth and fifth are a little shorter than the third;
the succeeding ones gradually decreasing, as in the other species of
this genus: all the spines are moderately slender, the anterior ones
slightly arcuate, with scarcely any appreciable difference in the
degree of stoutness in the first four. Anal with the first spine
extremely short; the second obviously stouter than any of the dorsal
spines, but much shorter, being only half the length of the second
dorsal spine, or one-third the depth of the body; the third spine is
a trifle longer than the second, but much slenderer. Caudal deeply
forked; the lobes worn at the tips in this specimen, but their
length, when perfect, probably about one-fourth, or somewhat less,
of the entire length of the fish. Pectorals narrow and pointed, a
little shorter than the head, and contained four and a half times in
the entire length; fifth ray longest. Ventrals a little behind the
pectorals, and not more than two-thirds their length, or scarcely so
much; the spine a little shorter than the soft rays, and of about
the same degree of stoutness as the dorsal spines. Elongated scale
in the axillæ of the ventrals about three-fourths the length of the
spine, of a narrow lanceolate form, ending in a very fine point.
D. 9/10; A. 3/7; C. 17, &c.; P. 14; V. 1/5.
Length 3 inc. 6 lines.
COLOUR.—Not noticed in the recent state. In spirits, it appears of a
uniform silvery, with the back and upper part of the sides inclining
to dusky olive: no bands or any particular markings: fins pale.
Habitat, Rio de Janeiro.
The species of this genus are numerous, and extremely similar to each
other. Many of them appear to rest on characters taken simply from the
relative lengths and degrees of stoutness of the dorsal and anal spines.
This renders it extremely difficult to identify single specimens.
Perhaps I am wrong in referring the one described above to the _G. Gula_
of Cuvier and Valenciennes; but it makes so near an approach to that
species, that I hardly dare characterize it as distinct. It cannot be
the _G. Aprion_ of those authors, which is closely allied to the _G.
Gula_, and is found on the same coasts, since its teeth are so very much
finer: the caudal also is not scaled. It is small, but Cuvier and
Valenciennes state that none of their specimens of the _G. Gula_ exceed
five inches. Mr. Darwin took it in a salt-water lake, Lagoa de Boacica,
at Rio de Janeiro.