is made by the arrangement of the teeth in a single row both upon
the roof and at the margins of the mouth. The intermaxillary bones
are produced backwards, and the single series of small pointed teeth
which they support is opposed to a similar series upon the premandi-
bular bones below; to which elements of the lower jaw the teeth are
henceforth confined in the class of reptiles. The palatal teeth form a
single row on each of the broad bones, which correspond with those
described by Cuvier as the divided vomer in the higher Batracbians,
and extend backwards upon the pterygoids, which support a few
teeth.
79. Proteus.—The Proteus anguinus, (PI. 62, fig. 3 .) though retaining
like the three preceding genera its external gills, offers a further
advance to the dental characters of the higher Batrachians, especially of
the amphiuma. The alveolar border of each intermaxillary bone is
armed with a row of eight or ten minute and fine sharp-pointed teeth :
each premandibular bone supports a greater number of similar but larger
teeth, likewise arranged in a single row. The palatine bones, or the
two vomers of Cuvier, support a row of denticles, similar and parallel
to the intermaxillary crescentic series : but the horns of the palatal
dental crescent are continued much further back, and terminate as in
the menobranchus, on the anterior part of the pterygoid bones : each
half of the crescentic, or chevron shaped series, contains twenty-four
teeth. The superior maxillary bones are represented in the proteus
by mere cartilaginous rudiments.
80. Amphiuma.—The Amphiume, like the proteus, presents the
batrachian disposition of the teeth in a single close-set series along
the alveolar border of both upper and lower jaws ; but the upper series
is extended along well developed maxillary, as well as intermaxillary
bones; and in the extent of the maxillary and palatal series of
teeth, especially in one species of amphiume (Amph. tridactylum),
there may be discerned the indication of a character which is of much
interest in regard to the affinities of an extinct race of gigantic Batrachians
with biconcave vertebrae. The palatal teeth in the amphiume
are arranged in a single close-set row along the lateral margins of the
vomer, meeting at an acute angle at its anterior part, from which the
series extends backwards on either side nearly longitudinally and
parallel with the maxillary teeth. All the teeth are conical, pointed,
slightly curved backwards and inwards; their points glisten with a
yellow metallic lustre, whence the name of Chrysodonta proposed for
this genus by Dr. Mitchell. (1)
The Amphiuma means has twenty teeth on each side of the upper
jaw, of which fifteen or sixteen are attached to the superior maxillary
and four or five to the intermaxillary bones : it has sixteen teeth on
each side of the lower jaw. There are fourteen or fifteen teeth in
each of the vomerine series.
The Amphiuma tridactylum (PI. 62, fig. 7) has four intermaxillary
and thirty-one or two maxillary teeth on each side of the upper jaw,
and twenty-four teeth on each side of the lower jaw. It has twenty-
six to twenty-eight teeth in each vomerine series.
81. Menopoma.—The Menopome (PI. 62, fig. 5 and 6), exhibits
the same essentially batrachian condition of the teeth as the amphiume,
but in their disposition, and in the division and form of the vomer,
it makes a nearer approach to the caducibranchiate group, and allies
itself most closely with the gigantic newt of Japan, (Sieboldtia,
Bonap.) and with that equally gigantic extinct species of newt, so
noted in paleontology, as the Homo diluvii testis of Scheuchzer.(2)
In the persistence of the branchial apertures, and the more complex
structure of os hyoides, the menopome, however, manifests its
generic distinctness from the Sieboldtia. The single close-set series
of small, equal, conical and slightly recurved teeth describes a semicircle
on both the upper and lower jaws : the row of similar but smaller
teeth on the anterior expanded border of the divided vomer runs
parallel with, and at a short distance behind the median part of the
maxillary series, (PI. 62, fig. 6). The premandibular teeth are received
into the narrow interspace between the two rows in the upper jaw when
the mouth is closed. The teeth of the menopome as of the amphiume
are anchylosed by their base and part of its outer side to a slightly
elevated external alveolar ridge.
82. Sieboldtia. — The perennibranchiate or fish-like Batrachians—‘
doubtful reptiles’ as they have been termed—lead by
(1) Medical Recorder, July, 1822.
(2) Philosophical Transactions, xxxiv, (1726), p. 38.