MARSUPIALIA. 
are adapted, the first for cropping the foliage of 
the gum-trees ( Eucalypti) and similar trees, 
and the others for bruising and masticating the 
same. The grinding surface of the molars ge- 
nerally presents four blunt tubercles. 
The Koala resembles in its dentition and in 
its diet and arboreal life the Phalangers and 
Petaurists. In the lower jaw the absence of 
teeth between the two large procumbent incisors 
and the false molars is constant ; in the upper 
jaw, however, the lateral or posterior incisors 
begin to exhibit the same diminution of size as 
the corresponding teeth in the lower jaw of 
some of the Phalangers, while the two anterior 
upper incisors present a proportional increase ; 
the canines correspond in feebleness and form 
with the small incisors. In the Wombat, the 
defective development to which the teeth be- 
tween the incisors and molars are subject in 
the Marsupial tribe, has reduced the dental for- 
mula of both jaws to the rodent type ; but the 
shape, comparative shortness, and procumbent 
position of the two large inferior incisors, and 
the three-sided figure of the opposing pair 
above, bespeak the marsupial character of which 
this genus offers so extreme a modification. 
The grinders, however, agree with those of the 
herbivorous rodents in the absence of fangs, 
arising from the uninterrupted growth and ossi- 
fication of their formative pulps; they offer 
also in both jaws an extreme degree of the cur- 
vature which characterises the molars of some 
herbivorous Rodents, as the Guinea-pig, and 
the great extinct gliriform Pachyderm, called 
Toxodon; but their chief distinctive peculi- 
arity is the marsupial excess of number already 
mentioned. 
With respect to the modifications of the 
teeth of the herbivorous Marsupials, it need 
only here be observed that the grinding surface 
of the true molars in the Kangaroos most re- 
sembles that which characterizes the same teeth 
in the Tapir, Dinothere, and Manatee. 
No Marsupial pessesses teeth composed of 
an intermixture of layers of dentine, enamel 
and cement throughout the crown, but the ex- 
ternal layer of coronal cement is very conspi- 
cuous in transverse sections of the teeth of the 
Marsupials, viewed with the microscope, and 
forms a thick layer on the outside of the crowns 
of the teeth in the genera Macropus, Phascol- 
arctus, and Phascolomys. 
The modifications of the tongue and soft 
palate have already been noticed. In two 
species of Marsupials I have detected cheek- 
pouches. In the Koala they are wide and 
shallow, situated one on each side of the upper 
lip; the orifice is opposite the first superior 
premolar, and leads forwards above a horizontal 
fold of the mucous membrane which attaches 
the upper lip to the side of the intermaxillary 
bone, separating this part of the cheek-pouch 
from the mouth. In the Perameles lagotis 
there are also two small fossze, one on the in- 
side of each cheek, about four lines in diameter, . 
and lined by a very distinct white epithelium. 
The fauces are wide in the Zoophagous, but 
narrow in the Entomophagous and Phytopha- 
gous Marsupials. 
Alimentary canal.—The esophagus in passing 
299 
through the chest recedes from the spine as it 
approaches the diaphragm, and is loosely con- 
nected with the bodies of the dorsal verte- 
bre by a broad duplicature of the serous 
membrane of the posterior mediastinum. In 
the Phalangers the esophagus terminates in the 
stomach almost as soon as it has pierced the 
diaphragm ; in the Opossums it is continued 
some way into the abdomen; in the Didelphys 
Virginiana, for example, for the extent of an 
inch and a half; in Did. brachyura, for half 
an inch. In the Kangaroos the abdominal 
portion of the esophagus is of still greater 
extent ; I have observed it five inches long in 
a male Macropus major. 
The inner surface of the cesophagus is gene- 
rally smooth, or disposed in fine longitudinal 
plaits ; but in the Virginian Opossum the ter- 
‘minal part of the cesophagus presents many 
transverse folds of the lining membrane analo- 
gous to, but relatively larger than those in the 
Lion and other Felines. I have not met with 
a like structure in the Phalangers nor in any 
other genus of Marsupials; what is more re- 
markable is that the transverse cesophageal rugze 
are not developed in the carnivorous Dasyures 
or Phascogales, where analogy would lead one 
to expect them, rather than in the insectivorous 
Opossums. 
The stomach presents three leading modifica- 
tions of structure in the Marsupialia; it is either 
simple, as in the Zoophagous, Entomophagous, 
and Carpophagous tribes; or is provided with a 
cardiac glandular apparatus, as in the Koala and 
Wombat; or is complicated by sacculi, as in the 
Poephagans. 
It might have been expected that the stomach 
would have exhibited some modifications in 
the development of the left or cardiac extremity 
comin with the differences of food and 
dentition observable in the large proportion of 
the Marsupial order, in which this viscus pre- 
sents its simple condition ; but this is not the 
case: the form of the stomach is essentially the 
same in the carnivorous Dasyure, the insecti- 
vorous Bandicoot, and the leaf-eating Phalan- 
gers. It presents a full, round, ovate, or 
sub-triangular figure, with the nght extremity 
projecting beyond and below the pylorus; the 
longitudinal diameter seldom exceeds the ver- 
tical or transverse by more than one-third ; often, 
as in Phascogale and Dasyurus viverrinus, by 
only one-fourth of its own extent; and the 
cesophagus enters at the middle of the lesser 
curvature, or sometimes nearer the pylorus, but 
always leaves a large hemispherical cul-de-sac 
on the left side. Daubenton has given illustra- 
tions of this characteristic form of the stomach 
in different species of Didelphys; it is here 
figured as it exists in the Phascogale (fig. 122). 
The stomach is relatively much more capacious 
in the carnivorous Marsupials than in the car- 
nivorous Placentals. Some slight modifica- 
tions occur in the disposition of the lining 
membrane; thus in the Phascogale I observed 
a series of very thick ruge radiating from the 
middle of the upper part of the ccecal end of 
the stomach, some of which were continued 
along the lesser curvature to the pylorus. Dr. 
Grant found, in the Perameles nasuta, that “ the 
