PLATE VII. FIG. 1. Lateral view twice nat. size.
FIG. 1_a_. Dorsal view nat. size.
FIG. 1_b_. Lateral view nat. size.
_A. corpore elongato, anticè octagono, posticè hexagono; vomere et
ossibus palatinis dentibus distinctis instructis; maxillis
subæqualibus; rostro ultrà fauces haud producto; mento et membranâ
branchiali cirratis: pinnis dorsalibus discretis; primâ radiis
gracilibus._
B. 6; D. 8–7; A. 8; C. 112/2; P. 14; V. ½.
Long. unc. 2. lin. 7.
[Illustration:
_Fish Pl. 7._
_W. Hawkins del^t._
]
_1. Aspidophorus Chiloensis._ _Twice Nat. Size._
_1a. 1b. „_ _Nat. Size._
_2. Agriopus hispidus._ _Twice Nat. Size._
_2a. „ „_ _Nat. Size._
_2b. „ „_ _Magnified Scales._
FORM.—More elongated than the _A. cataphractus_, which it somewhat
resembles in general appearance. Anterior portion of the body
octagonal, and the posterior, or all beyond the second dorsal and
anal, hexagonal. Head equally depressed as in that species; but its
breadth less, being only one-fifth of the entire length, caudal
excluded. Length of the head rather less than one-fourth of the
entire length. Depth at the nape rather less than one-seventh of the
same. Eyes relatively a little larger than in _A. cataphractus_;
their diameter one-fourth the length of the head; placed high in the
cheeks, and distant one diameter from the end of the snout. Upper
part of the orbit elevated into an osseous ridge on each side of the
crown of the head, with a spine at its anterior angle, and the ridge
itself terminating in a sharp, rather stronger, spine at the
posterior angle; both spines directed backwards. Space between the
eyes concave, equalling in breadth not quite one diameter of the
eye, with two longitudinal sharp ridges running respectively
parallel to the ridges of the orbits, but not nearly so much
elevated as these last; these ridges terminate posteriorly at a
groove, which runs transversely behind the eyes, separating the
vertex from the occiput. The snout presents the same four spines,
which are to be seen in the _A. cataphractus_, but it does not
project beyond the mouth. The lower margin of the suborbital
presents a somewhat irregular ridge formed by a series of bluntish
tubercles, the last of which terminates in a very minute spine
directed backwards. Limb of the preopercle with three diverging
smooth ridges, dilating at their extremities into three flattened
blunt points, which project a little beyond the membrane, but can
scarcely be called spines. Opercle with one ridge not so strongly
marked as those of the preopercle, and not terminating in any
distinct point, nor even reaching quite to the edge of the membrane.
Jaws nearly equal; but the upper one a very little the longest; each
with a narrow band of minute velutine teeth: a distinct chevron of
similar teeth on the front of the vomer, and a short imperfect row
on each palatine. Tongue smooth. Gill-opening large: the branchial
membrane not notched, but passing transversely over the isthmus, to
the edge of which it is nevertheless attached on each side. Chin
clothed with short fleshy cirri; also a few on the lower jaw and
branchial membrane; but they are much shorter, and less conspicuous
than in the _A. cataphractus_, especially on the branchial membrane,
where they are very sparingly scattered. The occiput presents the
four usual ridges formed of granulated tubercles; and between the
innermost pair there is also a much less conspicuous, but slightly
raised line running longitudinally down the middle: the two
innermost of the above ridges are nearly in a line respectively with
the two ridges of the orbit, behind which they commence, and they
would pass on to unite with the two dorsal carinæ were they not
separated from the latter by a deep transverse depression at the
nape: the two outermost of the occipital ridges commence behind the
eyes themselves, and terminate at the suprascapulars, each in a
sharp point directed backwards, but not prolonged into a spine. The
carinated scales which arm the body of this species, are more
sharply serrated than those of the _A. cataphractus_, the keels
terminating behind in hooked points; and the elevated lines which
form the striæ on each side of the keel are fewer in number and more
raised. The ridges which they form are also more marked, and the
second ridge on each side commences immediately behind the angle of
the opercle, instead of opposite the vent as in that species; so
that the whole body is perfectly octagonal from the gills to the
termination of the dorsal and anal fins:[11] at that point, the two
dorsal ridges and the two ventral unite respectively to form one, or
rather approximate so closely as to form but one in appearance; for,
if closely examined, there will still be found two parallel rows of
serratures. In each of the two uppermost or dorsal ridges, there are
twenty-seven scales, reckoning from the hollow at the nape to the
point where the ridges unite. In the second ridge (which extends, as
before observed, from the gills to the caudal) there are
thirty-eight. In the third, which commences behind the pectoral, and
extends in like manner to the caudal, there are thirty-five. In the
fourth, which commences on the breast, immediately behind the point
of attachment of the branchial membrane to the isthmus, there are
thirty, reckoning to behind the anal, where it unites with its
fellow to form one; between this point and the caudal there are ten,
the serratures of which are rather obsolete. The fourth pair of
ridges are throughout their course less sharply serrated than the
second and third pairs, and these last again rather less so than the
first or dorsal pair. Between the two ventral ridges, near their
commencement in front of the ventral fins, are six slightly serrated
scales (similar to those in the ridges) forming on the breast a
somewhat triangular patch, two single ones standing first, then four
others in pairs. The lateral line, which is catenulated as in _A.
cataphractus_, commences at the upper angle of the opercle, then
bends downwards to take a middle course between the second and third
ridges, which it preserves to the caudal. The first dorsal commences
behind the seventh scale in the dorsal ridges, or at about one-third
of the entire length; it is of the same form as in the _A.
cataphractus_, but contains more rays; its membrane terminates at
the fifteenth scale, and there are rather more than two scales
between it and the second dorsal, which last is rather shorter and
higher than the first. The rays of the first dorsal are not stouter
than those of the second, nor relatively stouter than those of the
_A. cataphractus_. The rays of the second dorsal are simple, with
the second and third rather longer than the first. The anal answers
to the second dorsal. The pectorals are rounded, and one-fifth of
the entire length. Ventrals very narrow, and scarcely more than half
the length of the pectorals. Position of the vent a little anterior
to a line connecting the extremities of the ventrals.
COLOUR.—(_In spirits._) Dusky grey above and on the sides, paler
beneath; with four broad transverse blackish fasciæ passing across
the back and down the sides as far as the third longitudinal ridge
of scales. The first fascia is in the region of the first half of
the first dorsal; the second at the commencement of the second
dorsal; the third near the end of the second dorsal; the fourth
half-way between the end of the second dorsal and the caudal; and a
little beyond this there is a faint trace of a fifth fascia. The
body is a little mottled in places with spots of the same dark
colour as the fasciæ, and the fins, with the exception of the
ventrals, are of the same hue.
Habitat, Chiloe, (West coast of S. America).
The absence of vomerine teeth has been considered by Cuvier as one of
the characters serving to distinguish _Aspidophorus_ from _Cottus_; but
as these teeth are very distinctly developed in the present species, we
must rather dwell upon the large keeled sharp-pointed scales, which
envelope the body in a kind of mail, and, as Dr. Richardson
observes,[12] “give the _Aspidophori_ a totally different aspect from
the _Cotti_.” Indeed on equally strong grounds as those on which Cuvier
has separated _Pinguipes_ from _Percis_ and _Prionotus_ from _Trigla_,
the present species, which possesses both vomerine and palatine
teeth,[13] might be made a distinct genus from _Aspidophorus_, or at
least considered as one of its subgenera. But in the present uncertain
state of our knowledge with respect to the exact value of this
character,[14] and from the general resemblance of the _A. Chiloensis_
in all its principal characters to the other species of this genus,[15]
I have not thought this step necessary.
This species was taken by Mr. Darwin at Chiloe. There are two specimens
in the collection. The second differs from the one above described, only
in having one ray less in the first dorsal, and two more carinated
scales in each of the dorsal ridges. Independently of its having
vomerine and palatine teeth as above noticed, this species will not
enter into any of Cuvier’s sections of the genus _Aspidophorus_, but
combines in itself the characters of his first and third; the dorsals
being separated by nearly three scales, the jaws being very nearly
equal, the rays of the first dorsal not stouter than those of the
second, and the throat being bearded.