fishes. In every subgenus teeth are present on the intermaxillary,
premandibular, vomerine, branchial and pharyngeal bones, but not
on the hyoid or palatine bones ; and in all, the teeth are simple,
conical, and sharp-pointed; varying only in regard to size and degree
of curvature.
They are distributed over a broad band upon the upper jaw,
and over a narrower band along the lower jaw in the cod (Morrhua
vulgaris), the haddock (Mor. Merlangus), the dorse (Mor. callarias),
in which the exterior row is the largest in the upper teeth
and the interior row in the lower ones. In the pout fMorrhua
lusca), the ling (Lota Molva), and the whiting {Merlangus vulgaris),
there is only a single row of long and large teeth in the
premandibulars. The exterior row of larger intermaxillary teeth
are more distinctly separated from the smaller posterior teeth of
the same bones in the haddock, in order to receive in their
interspace the points of the single row of premandibular teeth when
the mouth is closed; but in the ling the upper teeth are numerous
and of small size. In the hake {Merlucius vulgaris), there is a single
row of slender and sharp teeth in both the upper and lower jaws.
The tadpole-fish {Raniceps trifurcata), has two rows of sharp teeth in
the premandibular bones, and numerous smaller, but not serial teeth
in the intermaxillaries. In the coal-fish {Merlangus carbonarius), the
torsk {Brosmius vulgaris), and the rock-ling {Motella 5-cirrata), the
teeth are small and ranged in a band along both jaws. The vomerine
teeth in all the cod tribe are usually arranged in a transverse crescent
on the expanded anterior part of the bone.
All the teeth are less firmly attached to the bones in the Gadoids
than in other osseous fishes with laniariform teeth. In the cod-fish the
gelatinous conical pulp, after having formed the body of the tooth, is continued
in an uncalcified state, but condensed into ligamentous firmness,
from the base of the tooth to the alveolar margin of the jaw : ossification
then proceeds from the jaw along the ligaments towards the base
of the tooth, which, however, rarely become anchylosed to the ossified
ligaments. The teeth, therefore, are generally detached in the course
of macerating the head of the cod, and the broad alveolar margin of
the dentigerous bones is then covered by the ossified dental ligaments
in the form of truncated cylinders of various sizes, the largest being
most external in the intermaxillary and the reverse in the premandibular
bones. A group of smaller but similarly shaped cylindrical
processes for supporting the teeth are arranged in the form of a chevron
across the anterior extremity of the vomer in the cod, after similar
maceration. The branchial teeth are more firmly attached,
being anchylosed in small groups upon the short obtuse processes
of the branchial arches ; there is a double series of these dentigerous
tubercles along the concave margin of the second and third arches.
The upper and lower pharyngeal bones are beset with small
recurved laniary teeth, which are also more firmly fixed than those
on the vomer and jaws.
Retzius compares the dentigerous processes of these bones to
epiphyses, but I find that ossification is continued from the supporting
bone into them, and have never observed them in a detached state,
like the teeth themselves: he correctly describes their texture as
being, in the ling, intermediate between that of the bone and tooth.
In this species he describes the teeth as being “ semi-transparent, with
a covering of enamel upon the extreme points of such as are not too
much worn. This little covering of enamel is disposed upon the tooth
like the shoe of iron upon a spade, being continued from a transverse
edge forwards and backwards, but being in some produced into
a sharp point; the whiteness of the teeth is due to this substance.”(l)
The pulp-cavity of the fully-formed tooth in the cod is continuous
with the cavity of the supporting osseous cylinder to which it is
attached; it varies in size according to the age of the tooth, and
is, at length, reduced to a linear cavity extending along the middle
of the axis of the tooth. Processes of the pulp are conveyed by
medullary canals which diverge from all parts of the main central
cavity into the substance of the dentine ; these are about ^th of an
inch in diameter at their origin, but they quickly divide, and their
branches form anastomoses with those of the neighbouring tubes ; the
loops, thus formed by the smaller terminal branches, constitute a
well-defined boundary between the coarse central and the fine
external dentine. In this latter layer the calcigerous tubes, which
(1) Loe. cit. p. 268.