_A. corpore ovali, altitudine prope tertiam partem longitudinis
æquante: ventre carinato, serraturis, præsertim inter pinnas
ventrales et analem, acutis: maxillis subæqualibus, edentulis:
preoperculo venoso; operculo striato: squamis pectinatis: pinnis
ventralibus paulo ante dorsalem exorientibus._
D. 16; A. 21; C. 19, &c.; P. 17; V. 7.
LONG. unc. 12.
FORM.—Of an oval compressed form, the depth very considerable,
equalling very nearly one-third of the entire length. Head contained
about three times and three quarters in the same. Abdomen sharply
carinated, with strong serratures, especially between the ventrals
and anal. Jaws nearly equal, perhaps the lower one a little the
longest; intermaxillary deeply notched; no apparent teeth anywhere.
Eyes rather high, partly covered both anteriorly and posteriorly by
a membranaceous veil; their diameter about one-fifth the length of
the head; more than one diameter between them and the end of the
snout. Subopercle obliquely rounded off at bottom, but the curvature
of the posterior margin of the opercle and subopercle taken together
not very considerable. Preopercle marked with vein-like
ramifications; opercle similarly veined, and also striated below, as
in the species last described, though more finely. Scarce any trace
of a lateral line.
Scales moderately large, thin and membranaceous. One from the middle
of the side of a sub-oblong form, the hinder angles rounded, its
length only two-thirds of its breadth; the greater portion of the
surface marked with exceedingly delicate striæ, scarcely visible
without a strong lens, the anterior margin pectinated, and with a
slightly projecting lobe in the middle. The scales as they approach
the tail, become longer in proportion to their breadth, the basal
margin more rounded, and sometimes with a strongly projecting lobe
in the middle. The pectinations are longest on the scales covering
the nape.
The dorsal commences a little behind the middle point of the oval of
the body, and the ventrals are attached a little in advance of that
fin. The anal commences a little behind the termination of the
dorsal, and reaches to the commencement of the fleshy part of the
tail: the last ray in both dorsal and anal is slightly lengthened
beyond the preceding ones. The pectorals reach to the ventrals, and
are contained about once and two-thirds in the length of the head.
Caudal deeply forked; the lower lobe a little longer than the upper
one: the base appears to have been covered with minute scales. Above
the pectorals is a thin membranaceous lanceolate scale, more than
half the length of the fin: a somewhat similar scale in the axillæ
of the ventrals, but shorter in proportion; another below those
fins.
COLOUR.—“Body silvery: dorsal scales iridescent with green and copper:
head greenish: tail yellow.”—D.
A _second specimen_ agrees with the above in form, but is smaller,
measuring only 7½ inches. The colours, when recent, according to Mr.
Darwin’s notes, were as follows:—“Scales silvery iridescent; back
especially greenish; caudal fin yellow: remarkable for a circular
dark green patch behind the gill-cover.”—D.
Habitat, Bahia Blanca.
This species was caught by Mr. Darwin in the net, on a sandbank, at
Bahia Blanca. It is well characterized by its strongly-pectinated
scales, and does not appear to have been noticed by authors; though it
would seem in that respect to have some affinity with the _Clupea
fimbriata_ of Bowdich.[40]