Scams spinidens, Quoy and Gaimard, the anterior denticles are imbricated
or arranged like tiles in several rows, and the lateral ones in
the upper jaw are always separated and pointed. There is, also, an
internal row of very small intermaxillary teeth. Cuvier has grouped
together the parrot-fishes with this type of dentition under the subgeneric
term Callyodon, which was applied by Gronovius to all the
Scari.
The parrot-fishes, like the wrasses, have no teeth on the superior
maxillary, palatine or lingual bones\, but are provided with
strongly developed pharyngeal bones peculiarly well furnished with
an apparatus of teeth for comminuting the coarse fragments of
blended gelatinous and calcareous matters, which the protruded jaws
are organised to break oflf.(l)
Certain parrot-fishes in which the tooth-paved mandibles are
more slender and spoon-shaped than in the true Scari, and henee
probably subsisting on a diflferent diet than the madrepores on which
such species browse, have the pharyngeal bones provided, as in the
Labri, with numerous obtuse rounded denticles, but more closely
packed together; these parrot-fishes constitute the sub-genus Odax
of Cuvier.
The typical Scari have both upper and lower pharyngeal bones
paved with strong thick lamelliform teeth, set vertically and transversely
in the opposed surfaces of those bones. It is the posterior 1
(1) The general assertion by Cuvier, that the Scari, like the terrestrial ruminants feed
exclusively on vegetables, “ comme les ruminans terrestres, le Scare ne se nourrissait que de
végétaux,” (Cuvier, Histoire Naturelle des Poissons, tom. xiv, p. 100)—must be received with a
certain restriction, although coming from an anatomist who so well understood, and who was
the first to describe intelligibly, the plan and principle of the powerful and complicated dental
armature of the parrot-fishes. It is true that Aristotle, in the passage quoted by Cuvier;
asserts that “ the Melanurus and the Scarus subsist on sea-weed b ut then the Greek Naturalist
also pushes the analogies of the Scarus to the terrestial rufninants so far as to
quote, and sanction, the belief that this fish actually ruminated. Some of the species
with weaker and sharper-edged mandibles may crop the sea-weeds as well as other substances,
b ut both Commerson and Dussumier testify to the coral-feeding habits of the parrot-
fishes of the Isle of France and the Séchelles, etc. Mr. Darwin, who dissected several Scari
soon after they were caught, found their intestines laden with nearly pure chalk, and observed
that such, likewise, was the naturè of their excrements ; whence he classes these fishes among
the geological agents to which is assigned the task of converting the skeletons of the Lithophytes
pair of the upper pharyngeals which are thus armed; the lower
pharyngeal bone is single. (1)
The superior dentigerous pharyngeals present the form of an elongated,
vertical, inequilateral triangular plate ; the upper and posterior
margin is sharp and concave ; the upper and anterior margin forms
a thickened articular surface, convex from side to side, and playing in
a corresponding groove or concavity upon the base of the skull; the
inferior boundary of the triangle is the longest, and also the broadest;
it is convex in the antero-posterior direction and flat from side to
side. It is on this surface that the teeth are implanted, and in most
species they form two rows ; the outer one consisting of very small
teeth, the inner one of large teeth. These present the form of compressed
conical plates or wedges, with the basis excavated and the
opposite margin moderately sharp, and slightly convex to near the
inner angle which is produced into a point: these plates are set nearly
transversely across the lower surface of the pharyngeal bone, and are
in close apposition, one behind the other : their internal angles are
produced beyond the margin of the bone, and interlock with those of
the adjoining bone when the pharyngeals are in their natural position ;
the smaller denticles of the outer row are set in the external interspaces
of those of the inner row, (PI. 51, fig. 2).
The single inferior pharyngeal bone consists principally of an
oblong, dentigerous plate, of the form represented in Plate 51, fig. 3 ;
its breadth somewhat exceeds r that of the conjoined dentigerous
surfaces of the pharyngeals above, and it is excavated to correspond
with their convexity. This dentigerous plate is principally supported
by a strong, slightly curved, transverse osseous bar, the extremities of
which expand into thick obtuse processes for the implantation of
the triturating muscles. A longitudinal crest is continued downwards
and forwards from the middle line of the inferior pharyngeal plate,
anterior to the transverse bar, to which the protractor muscles are
attached.
A longitudinal row of small oval teeth alternating with the
large lamelliform teeth, like those of the superior pharyngeals, bounds
(!) Cheselden has given a figure of this bone at the end of the first chapter of his
I Osteography.”