2 FORM.
has attracted the attention of most comparative anatomists, and yet
such is the rapidity with which new species, either of the present
or a past creation, are added to the catalogues of the ichthyologist,
that this part of the subject is far from being exhausted. All the
known differences which the teeth of fishes present in this respect I
may, however, be referred to modifications, either of the cone, the
plate, the prism or the cylinder.
The conical teeth may be slender, sharp-pointed, and so minute,
so numerous, and closely aggregated as to resemble the plush or pile of
velvet; these will be termed villiform teeth, they are the dents en velours
of Cuvier, and are sometimes so short as to be more easily felt than
seen: when the teeth are equally fine and numerous but longer, they will
be called ciliiform teeth : when long and slender, but a little stronger,
they are the dents en brosse (brush-teeth) of Cuvier. Conical teeth as
close-set and sharp-pointed as the villiform teeth, but of larger size, are
the dents en rape, or en cardes of the French anatomist. These modifications
of the whole or a part of the dental series are common to
a great number of fishes. The perch has all its teeth en velours; the
pike presents the rasp-like teeth on the posterior part of the vomer ;
the armature of the palate bone of the silurus (PI. 1, fig. 1,) as well
as that of other bones of the mouth of the same fish, presents all the
gradations between the dents en velours, and the dents en cardes.
The conical teeth may be so long and slender as to resemble
bristles, as in the chsetodonts; (PL 1, fig. 2.) These setiform teeth
are sometimes bifurcate at their free extremity, as in the genus
Citharina; or they may terminate in three diverging points, as in
the anterior maxillary teeth of the genus P'latax (PI. 1, fig. 2*), and
here the cone merges into the long and slender cylinder. Or the
elongated cone may be compressed into a slender trenchant plate;
and this may be pointed, recurved, or even barbed like a fish hook, as
in the Trichiurus (PI. 1, fig. 8,) and some other scomberoid fishes ; or
it may be bent upon itself like a tenter-hook, as in the Pimelipterus
and Gonyodontes. In other species as in the bonito, (PI. 1, fig. 3,) the
conical teeth present a progressive thickening of the base, and this
modification being combined in certain predatory fishes with an
increase of size and a slightly recurved direction, they resemble the
FORM. 3
1 laniary or canine teeth of the carnivorous quadrupeds. Of this kind
■ are the larger teeth of the pike and Rhizodus (PI. 35), and the
■ anterior teeth of the Dentex, (PI. 41). A moderately long, stout
land more or less straight cone is a form exemplified in the anterior
■ teeth of the wolf-fish, (PI. 60 & 61,) and the transition by progressive
■ blunting, flattening and expansion of the apex is very gradual from
■ this form of the cone to the thick and short cylinder, such as is seen
■ in the posterior teeth of the wolf-fish, and similar grinding or
■ crushing teeth of many other existing genera. The working surface
■ of these short cylindrical teeth may be rounded as in the sheep’s-
Ihead-fish (Sargus, PI. 42, fig. 1,) or flattened as in the pharyngeal
■ teeth of the wrasse, {Labrus, PI. 45, fig. 4). Sometimes the hemi-
Ispheric teeth are so minute and numerous as to give a granulated
■ surface to the part of the jaw to which they are attached (PI. 45, fig. 1).
A progressive increase of the transverse over the vertical dia-
Imeter may be traced in the molar teeth of different fishes, and
■ sometimes in those of the same individual, until the cylindrical form
■ is lost in that of the depressed plate. Of this change we have a good
■ example in the posterior teeth of the gilt-head (Chrysophrys), when
■ arrived at maturity, and likewise in the fossil genus Placodus,
I (PI. 30). The dental plate, instead of offering the cylindrical form,
■ may be elliptical, oblong, square, triangular, semilunar, sigmoid,
land with the grinding surface variously sculptured. The broadest
land thinnest depressed laminae are seen in the component denticles
■ of the molar tubercle of the diodon, and in the teeth of the Phyllodus.
The incisors of the sargus, (PI. 1, fig. 13,) flounder, and some
■ other fishes present the compressed laminated form, at least, in the
■ protruded coronal portion. Numerous wedge-shaped dental plates
■ are set vertically in the pharyngeal bones of the Scarus or parrot-
■ fish. A thin lamella, slightly concave like a finger-nail, is the sin-
■ gular form of the tooth of an extinct genus of cartilaginous fishes,
■ which I have, on that account, named Petalodus, (PL 22, figs. 2, 3, 4.)
■ Sometimes the flattened incisive crown is notched in the middle of
■ the cutting edge, as in the incisors of the species of bream (Sargus
■ «mmacMZafMs) figured in Pl. 1, fig. 9. Sometimes there is a double
■ notch rendering the crown of the incisor trilobate, as in the genus
b 2