276 
elearly exemplified in the fossil jaw from the 
Stonesfield oolite, in the British Museum, re- 
presenting the extinct Marsupial which I have 
termed Phascolotherium Bucklandii. In the 
Opossums the internal angular process is tri- 
angular and triedral, directed inwards, with 
the point slightly curved upwards, and more 
uced in the small than in the large species. 
n the Dasyures it has a similar form, but the 
apex is extended into an obtuse process. In 
the Thylacine the base of the inverted angle*is 
proportionally more extended, and a similar 
structure is presented by the fossil Phascolo- 
there. In the Perameles the angle of the jaw 
forms a still longer process; it is of a flat- 
tened form extended obliquely inwards and 
backwards and slightly curved upwards. It 
presents a triangular, slightly incurved, and 
pointed form in the Petaurists, in which it is 
longest and weakest in the pigmy species, 
(Acrobates, Desm.) It is shorter and stronger 
in the Myrmecobius (fig.97). In the Po- 
toroos and Phalangers the process 
is broad with the apex slightly de- 
veloped; it is bent inwards and 
bounds the lower part of a wide 
and deep depression in the inside 
of the ascending ramus. In the 
great Kangaroo the internal margin 
of this process is curved upwards, 
so as to augment the depth of the 
internal depression above men- 
tioned. The internal angular pro- 
cess arrives at its maximum of 
development in the Wombat, 
(fig. 94,) and the breadth of the 
base of the ascending ramus very 
nearly equals the height of the 
same part. This broad base also 
inclines downwards and outwards 
from the inflected angle, and the 
2 same uliarity occurs in the 
geew soi, JAW of the Phascolothere. In 
7 “the Koala the size of the process 
in question is also considerable, but it 
is compressed, and directed backwards with 
the obtuse apex only bending inwards, so 
that the characteristic flattening of the base 
of the ascending ramus is least marked in 
this species. There is no depression on the 
inner side of the ramus of the jaw in the Koala, 
but its smooth surface is simply pierced near 
its middle by the dental artery. The surface 
of the external muscular depression bounded 
below by a broad angular ridge, as above de- 
scribed, is entire in the Dasyures, Opossums, 
Bandfeoots, Petaurists, and Phalangers; but 
in the Wombat the outer surface of the as- 
cending ramus is directly perforated by a round 
aperture immediately posterior to the com- 
mencement of the dental canal:* the corres- 
ponding aperture is of larger size in the Kan- 
garoo. But in the Potoroos both the external 
and internal depressions of the ascending ramus 
lead to wide canals, or continuations of the 
wide depressions which pass forwards into the 
Fig. 97. 
* A bristle is represented passing through this 
aperture in fig. 94, 
MARSUPIALIA. 
substance of the horizontal ramus, and so 
uniting into one passage, leave a vacant spa 
in the intervening bony ee Pe is stru 
ture, if it had been observed only in the jaw 
a fossil Marsupial, would have supported ; 
argument for its Saurian nature, more cogs 
than any that have been adduced in the ¢ 
cussion of the Stonesfield fossils, on account 
the analogous vacuity in the jaw of the C 
codile. 
The commencement of the dental cana! 
the Potoroos and Wombat is parallel with 
beginning of the molar series, and it ha 
same relative position in the Stonesfield | 
supials; but in the other carnivorous and 
sectivorous species the dental foramen is pla 
further back. In the Wombat a vascular groc 
is continued from the foramen along the in 
side of the ramus of the jaw as in the Ste 
field fossils; and a corresponding but w 
groove is present in the lower jaw of the WV 
mecobius. In the Thylacine and Ursine 
syures and their fossil congener the Phase 
there, the condyle of the lower jaw is pla 
low down, on a level with the molar ser 
it is raised a little above that level in the su 
ler Dasyures and Opossums, and ascen¢ 
proportion to the vegetable diet of the s 
cies. J 
In all those Marsupials which have fi 
very small incisors the horizontal rami of 
jaw converge towards a point at the symphi 
The angle of convergence is most in 
Wombat, and the gradual diminution in 
size of the rami as they approach this pa 
most marked and direct. The internal sur 
of the symphysis menti is almost horizor 
and is convex from side to side in the inte 
between the molars and incisors. The 
becomes obliterated in aged individuals. 
is also wholly obliterated in the skull | 
Koala now before me; in all the other Mi 
pial crania which I have examined, the | 
of the lower jaw are disjoined at the s 
physis ; and in the Opossum, both the rat 
the lower jaw and all the bones of the face 
remarkable for the loose nature of their 
nection. 3 
Vertebral column.—The vertebral colut 
divisible in all the Marsupials into the | 
classes of cervical, costal, lumbar, sacral, 
caudal vertebra. The cervical vertebrae | 
riably present the usual number, seven 
the usual character of the perforation of 
transverse process, or rather the presen¢ 
the upper and lower transverse processes, 
the union of their outer extremities with 
dimental rib. I found the cervical ribs ¢ 
dentata distinct and unanchylosed in a m 
Perameles. In the Dasyures, Opossums, 
dicoots, and Phalangers, the seventh ce 
vertebra has only the upper transverse pro 
and consequently wants the character ol 
perforation, as in many of the ordinary Mai 
malia. In the Petaurists, Koala, ” yom 
Potoroos, and Kangaroos, the seventh vert 
is perforated like the rest. But in 
garoo both the dentata and atlas have the tt 
> 
verse processes grooved merely by the ¥ arte 
