298 
angle of the jaw. The preceding description is 
taken from a dissection of the Koala. The 
masticatory muscles of the Wombat differ only 
in their relative proportions ; the masseter in 
this gliriform Marsupial is single, nting no 
trace of that subdivision and modified attach- 
ments which adapt it to the protraction of the 
lower jaw in the true Rodents, and accordingly 
the structure of the joint of the lower jaw of 
the Wombat exhibits, as already described, a 
corresponding difference from the Rodent 
type. 
vihere is no toothless genus among the true 
Marsupials, unless the Monotremes which re- 
present the Edentate order of the Placental 
Mammalia be regarded as modified Marsupials. 
Molar and incisor teeth are present in both 
jaws in every true Marsupial species ; the ca- 
nines are but feebly represented in many, as the 
Phalangers, Petaurists, &c. are wanting in the 
lower jaw in the Potoroos and Koala, and in 
both jaws in the Kangaroos and Wombat. The 
grinders, on the other hand, present their most 
complicated structure in these last cited herbi- 
vorous genera. 
The Dasyures and Thylacine offer the carni- 
vorous 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 Marsupial carnivorous 
genera, as is expressed in the dental formule 
already given. 
The canines are as formidable for their size, 
shape, and strength in the Thylacine and Ur- 
sine Dasyure, as in the Dog or Cat, and in a 
fossil species of the latter genus ( Dasyurus 
laniarius ),* which co-existed, in ancient Aus- 
tralia, with herbivorous Marsupials of greater 
size than now inhabit that continent, these 
teeth were as large as in the Leopard. In 
the Thylacine the points of the lower ca- 
nines are received in hollows of the intermaxil- 
lary palatal plate when the mouth is closed, 
and do not project, as in the carnivorous pla- 
centals, beyond the margins of the intermaxil- 
laries. 
In some of the smaller species of the carni- 
vorous group, as the Phascogales, the canines 
lose their great relative size, and the molar 
teeth present a surface more cuspidated than 
sectorial: there is also an increased number of 
teeth, and as a consequence of their more equa- 
ble development they have fewer and shorter 
interspaces. Thus the Phascogale penicillata 
has, as Mr. Hunter observed, “a mouth full of 
teeth,” and these are adapted for the capture 
and mastication of insects and other small and 
low organized animals. 
In the Opossums the canines still exhibit a 
superior development in both jaws adapted for 
the destruction of living prey, but the molars 
have a conformation different from that which 
characterises the true flesh-feeders, and they 
consequently subsist ona mixed diet or lower 
organized animals; some, as the web-footed 
Cheironectes, betake themselves to the water, 
* See Major Mitcheli’s Australia, vol. ii. 
MARSUPIALIA. 
and prey, like the otter, on fish; others 5 
about the sea-shore and subsist on crust 
as the Didelphys cancrivora. 
The Perameles are for the most part in: 
vorous ; the incisors are always very small, 
molars generally multicuspidate; some species, 
as Per. nasuta, have the canines not more dé 
veloped than the premolars, which they clos 
resemble ; but in others, as the Per. lagoti 
they are proportionally as large as in 
Opossums, and the inferior ones are cor ; 
in the same position when the mouth is closes 
as in the Thylacine. But the Per. lagotis, im- 
stead of exhibiting a corresponding approac¢ 
in the structure of the molars to a carni 
diet, have these unerring indicators of the na 
ture of the food terminated by a broad oblique 
flattened surface, adapted to the trituration 6 
farinaceous vegetable roots, the destruction: 
which is confidently attributed to this specie 
of Bandicoot by the colonists of Swan River 
The interesting genus Myrmecobius 
in the small size and scattered dis 
tion of its teeth, the nearest approach amon 
the Marsupials to the edentate group of th 
Placental Mammalia ; the multicuspidate strue 
ture of the molar teeth, and their small | 
indicates that the Myrmecobius feeds 
on the weaker insects which are implied b 
its generic name. It is important to notice 
that in many of the Marsupials there is a 
inconstancy in the number of teeth in 
of the same genus, and sometimes even in 
individuals in the same species; this at least 
appears to be the case in the Myrmecobius, in 
which, of three specimens examined, identical 
in all other respects, one had forty-eight, the 
other fifty-two, and the third fifty teeth. We 
have already pointed out the variety which 
tains in the spurious and true molars of 
Phalangers and Petaurists. The prominent 
feature in the change from the carnivorous to 
the herbivorous type of dentition is the ine 
nate development of the two middle inciso1 
the lower jaw, at the expense, as it would se 
ofthe posterior ones. In the Phalangista 
e. g. six incisors are always present in the le 
jaw, but only the first two have any functi 
character: the canine tooth again offers neit! 
a form nor size by which it can be distinguis 
from the spurious molars; in the other 
supials with the same characteristic modi 
tion of the hinder feet, including the Petauri 
with the Phalangers, the small posterior incis¢ 
are wanting wholly or in part; the canines seem 
also to be lost, and the spurious molars are 
fewer, but variable in number. This incon 
stancy is not to be wondered at in teeth whi 
have too simple a form and too insignificant a 
size to exercise any influence on the habits and 
economy of the species; and it would seem to— 
be lost labour in the zoologist to attempt to 
found generic distinctions, and invent new — 
names for the species in which these insignifi- 
cant varieties are presented. The six incisors 
of the upper jaw and the two anterior ones in 
the lower jaw, with the true molars in both 
jaws, present a constancy of character and a 
functional importance in their development in 
all the Phalangers and Petaurists. These teeth 
ro 
r 
