In the Paralepis, the intermaxillary teeth are so small that they
are indistinguishable without the aid of a lens ; thus magnified, they
are seen to be very numerous and close-set, like the teeth of a saw.
The premandibular and palatine teeth, on the contrary, are large,
but slender, recurved and sharp-pointed, set wide apart, with smaller
teeth in the interspaces. There are no teeth on the vomer or
tongue.
52. Sphyrcena.—The most formidable dentition exhibited in the
extensive Scomberoid family of the system of Agassiz is that which characterizes
the Sphyrcena, and some extinct fishes allied to this predatory
genus. In the great barracuda of the southern shores of the United
States, {Sphyrcena Barracuda, Cuv.) the lower jaw contains a single row'
of large, compressed, conical, sharp-pointed, and sharp-edged teeth,
resembling the blades of lancets, but stronger at the base. (1) The
two anterior of these teeth- are twice as long as the rest, but the
posterior and serial teeth gradually increase in size towards the
back part of the jaw ; there are about twenty-four of these piercing
and cutting teeth in each premandibular bone. They are opposed to
a double row of similar teeth in the upper jaw, and fit into the
interspace of these two rows, when the mouth is closed. The outermost
row is situated on the intermaxillary, the innermost on the
palatine bones ; there are no teeth on the vomer or superior maxillary
bones. The two anterior teeth in each intermaxillary bone
equal the opposite pair in the lower jaw in size; the posterior teeth
are serial, numerous and of small size ; the second of the two anterior
large intermaxillary teeth is placed on the inner side of the commencement
of the row of small teeth, and is a little inclined backwards.
The retaining power of all the large anterior teeth is increased
by a slight posterior projection, similar to the barb of a fish hook,
of the " Alepisaurus” most of the foregoing details of its dental organs are derived, observes,
with respect to the successors of the larger palatine teeth, “ Whether they were originally,
like the others, fixed, and are merely loose from injury or fracture, or are properly moveable and
free, I can scarcely venture to decide. At first sight and from the way in which they lie
amongst the loose gelatinous integuments of the palate, with no appearance of a regular attachment
by the base, their condition seems the effect of accident.”—Transactions of the Zoological
Society, vol. i, p. 396.
(1) PI. 1, fig. 4, and PI. 53, fig. 1.
but smaller. The palatine bones contain each nine or ten lancet
shaped teeth, somewhat larger than the posterior ones of the lower
jaw. All these teeth afford good examples of the mode of attachment
by implantation in sockets, which has been denied to exist in
fishes. (1)
The loss or injury to which these destructive weapons are liable
in the conflicts which the sphyrsena wages with its living and struggling
prey, is repaired by an uninterrupted succession of new pulps
and teeth. The existence of these is indicated by the foramina, (2)
which are situated immediately posterior to, or on the inner margin of
the sockets of the teeth in place; these foramina lead to alveoli of
reserve, in which the crowns of the new teeth in different stages of
development are loosely imbedded. It is in this position of the
germs of the teeth that the Sphyrsenoid fishes, both recent and fossil,
mainly differ as to their dental characters from the rest of the Scomberoid
family, and proportionally approach the Sauroid type. The
base or fang of the fully-developed tooth of the Sphyrsena is an-
chylosed to the parietes of the socket in which it is inserted. The
pressure of the crown of the new tooth excites absorption of the
inner side of the base of the old, which thus finally loses the requisite
strength of attachment, and its loss is followed by the absorption of
the old socket, as in the higher animals.
It is interesting to observe that the alternate teeth are, in general,
contemporaneously shed ; so that the maxillary series is always preserved
in an effective state. The relative position of the new teeth to
their predecessors, and their influence upon them, resemble, in the
Sphyrsena, some of the phenomena which will be described in the
dentition of the Crocodilian reptiles. To the crocodiles the present
voracious fish also approximates in the alveolar lodgment of the teeth,
but it manifests its ichthyic character in the anchylosis of the fully
developed teeth to their sockets, and still more strikingly in the
intimate structure of the teeth.
Few microscopic objects are more beautiful than a longitudinal
and transparent section of the tooth of the Sphyrsena, which accurately
Cl) Cuvier, Histoire Naturelle des Poissons, tom. i, p. 492.
(2) PI. 53, fig. 1, ajj p