posed in their alveoli in the left intermaxillary bone, are figured in
Plate 40, fig. 6 .
The number of the teeth is not constant in the genus Balistes, hut
in no species examined by me were the posterior teeth of the upper
jaw absent. In an Australian species, I found six teeth in the outer
row and four in the inner row of teeth in the upper jaw. The apices
of the mesial pair of the posterior row projected between those of the
first and second teeth of the outer row.
In all the file-fishes, the pharyngeal teeth are small, conical, laterally
compressed, curved and sharp-pointed; regularly arranged in two
rows upon the opposed margins of each of the two upper and lower
pharyngeal hones. A view of the upper and lower left pharyngeal
hones, in situ, is given in figure 2, Plate 40. The direction of the
curvature and the relative size of the anterior and posterior teeth are
reversed in the two bones, which thus form an admirable carding
machine for “ teazing” the bruised and coarsely divided sea-weeds
or other marine nutrient substances which the fish has obtained by
means of its large maxillary teeth.
Microscopical sections of these dense teeth in the Balistes forcipatus
present a structure so closely corresponding with that described by
Professor Retzius in the Balistes Vetula, that a better idea of it cannot
be conveyed than in the words of that excellent observer. He
says,(l) “ That the dentine (zahnknoche) of both the Balistes and
Sparus resembles most in internal structure that of the teeth of mammalia
and reptiles, being white and hard, like ivory, and displaying
under the microscope beautiful, regular, minute and parallel tubes.
These, in Balistes vetula, are of a Paris line(2) in diameter, and are
beautifully parallel, save in their last formed parts at the coronal end
of the pulp-cavity. Their undulations are long and slight. Their
interspaces are equal to their own diameter. The larger branches lie
close to the trunks, while the smaller ones generally bend away in a
(1) Muller’s Archiv. 1837, p. 523.
(2) The French inch of twelve lines is so nearly one-fifteenth more than the English inch,
that the conversion of the fraction of a French line into the fraction of an English inch by multiplying
the denominator of the former by Ilf, is sufficiently accurate -for all practical physiological
purposes; thus the calcigerous tube measuring -roVath of a Paris line, will be i x £ 5 0th of
*an English inch.
direction transverse to that of the main tubes, and towards the
root. The main tubes terminate near the superficies of the tooth
in hold parallel curvatures. The greater part of the tooth of this
fish is surrounded by a thick and dense enamel, into many parts of
which the tubes of the dentine appear to be continued; it is full of
fissures directed outwards. A kind of cement seems to surround the
base of the tooth.”
In his comparison of the structure of the enamel in the teeth of
different animals, Professor Retzius again refers to that of the Balistes,
and mentions the remarkable number and regularity of the fissures in
it, which, as he correctly states, somewhat resemble the tubes of the
dentine. “ The caementum is characterized by its large, and extremely
irregular cells, which are in many parts confluent, or communicate immediately,
with each other. The minute plexiform tubes have an
extremely irregular course. This coating of cement is very thin, and
seems to terminate below the margin of the enamel.” (l)
The similarity between the enamel and dentine of the file-fish, as
of the parrot-fish (see PI. 50), is not less close in regard to the organization
of their respective pulps, and their mode of calcification,
than in their microscopic structure when completely formed. The
caementum is the result of the ossification of the capsule which
includes the pulps of the dentine and enamel; and consequently it
corresponds in its coarse cellular structure with the rest of the
osseous system.
GONIODONTS.(2)<
32. The teeth of all the species of this family are long, slender,
filiform, or setaceous, and are bent like awls or tenterhooks, whence is
derived the name of the family. In some of the genera, the teeth of
the short and broad intermaxillaries are disposed in lines radiating
from behind towards the anterior margin, and are thus somewhat analogous
to the vertical rows in which the teeth of the sharks are arranged.
They further resemble the squaloid teeth in being attached,
not to the bone, but to the membrane investing the maxillae, and are
consequently moveable, both forwards and backwards.
(1) Loc. cit. p. 541. (2) Ta)viaf an angle, odsgf a tooth; PI. 48, figs. 1, 2 and 3.