molar series, none of them being displaced by vertical successors:
in this respect it manifests, like the Dugong, a cetaceous character,
and the more strongly, inasmuch as the number of molars successively
developed from before backwards is greater. The anterior
teeth are, however, displaced before the posterior ones are developed,
although they have no vertical successors, which circumstance is also
characteristic of the Elephant: the shape, the structure, and the mode
of implantation of the molars of the Manatee quite accord with the
pachydermal type, and herein more especially with the Dinotherium
and Tapir.
149. Halitherium(l).—An extinct herbivorous Cetacean has been
discovered in the miocene tertiary deposits which resembles the Dugong
in many parts of its skeleton, and in having permanent tusks in the
upper jaw I but which has complex, ridged, enamelled and many-rooted
molars as in the Manatee. The grinding surface of these .teeth
offers a slight modification of form; the superior molars when first
found detached were referred by Cuvier to the Hippopotamus dubius:
the lower molars to the Hippopotamus medius. The latter, PL 97,
fig. 5, have three tuberculate ridgesj the posterior one the smallest;
when worn down the crown of the tooth presents three pairs of
rounded lobes, and its margins are deeply festooned. The upper
molars (fig. 4) are more square-shaped, and the third tubercular ridge
is almost obsolete.
In a second species of the same or a nearly allied genus
(Halitherium Brochii) the crowns of the teeth are more rounded,
and beset with tuberculated mammiliform eminences. The entire
series on the left upper jaw is shown in PI. 97, fig. 1, and a similar
series of three molars in the left ramus of the lower jaw of the
Halitherium Cuvieri (fig. 2). The ultimate discovery and restoration
of a great part of the skeleton of one of the species (Halitherium
Cuvieri), and the determination of the small number of molar teeth
in both species, have established a very interesting intermediate genus
between Halicore and Manatus, and, at the same time, one which
pushed its infinities much nearer than either of the existing genera
towards the pachydermal aquatic genus Hippopotamus.
(1) Metaxythcrium, Christo], Cheirotherium, Bruno.
C H A P T E R V.
TEETH OF MARSUPIALIA.
150. Sarcophaga(l).—There is no toothless genus in the present
Order, unless the Monotremes or implacental Edentata be regarded as
modified Marsupials. Molar and incisor teeth are present in both jaws
in every true Marsupial species, but are relatively smaller in Tarsipes
and Myrmecobius, than, perhaps, in any other mammiferous quadruped •
the canines are but feebly represented in many, as the Phalangers
and Petaurists, are wanting in the lower jaw in the Potoroos and
Koala, and in both jaws of the Kangaroos and Wombat. The
grinders, on the other hand, present their most complicated structure
in these last cited herbivorous genera.
The Dasyures and Thylacine offer the carnivorous type of the
dental system, but differ from the corresponding group of the
Placental Mammalia in having the molars of a more uniform and
simple structure, and the incisors in greater number ; which number,
however, is different in the different predaceous genera, as is expressed
in the dental formulae.
That of the Thylacinus, or Dogheaded Opossum (PL 98, fig. 1),
is as follows :
Incisors — ; canines J—^; premolars — : molars — : = 46. 6~ 6 1—1 x 3—3 4—4
The incisors are of equal length and regularly arranged in the
segment of a circle with an interspace in the middle of the series
of both jaws. The external incisor on each side is the strongest.
The laniary or canine teeth are long, strong, curved, and pointed,
like those of the dog tribe; the points of the lower canines are
received in hollows of the intermaxillary palatal plate when the
mouth is closed, and do not project, as in the carnivorous Placentals,
beyond the margins of the maxillary bones. The spurious molars (p)
(1) By this name I first defined the present Tribe of Marsupial Animals in order to avoid
the confusion that might have arisen from the use of the word ‘ Carnivora’ usually applied to the
corresponding group in the Placental series of Mammalia.—-ZboZos icaZ Transactions, vol. ii, p. 315.