394 PROF. OWEN ON THE OSTEOLOGY 
inner side of the ramus of the jaw, as in the same fossils. In the Thylacine and Ursine 
Dasyures, and in their fossil congener the Phascolothere, the condyle of the lower jaw 
is placed low down, on a level with the molar series : it is raised a little above that level 
in the Opossums, and ascends in proportion to the vegetable character of the diet. 
In all those Marsupiata which have few or very small incisors, the horizontal rami 
of the jaw converge towards a point at the symphysis. The angle of convergence is 
most open in the Wombat, and the gradual diminution is most marked and direct. 
The internal surface of the symphysis menti is almost horizontal, and is convex from 
side to side in the interval between the molars and incisors. The suture becomes obli- 
terated in aged skulls. It is also wholly obliterated in the skull of a Koala now before 
me: in all the other marsupial crania which I have examined, the rami of the lower 
jaw are not anchylosed at the symphysis; and in the Opossum, both the ram of the 
lower jaw and all the bones of the face are remarkable for the loose nature of their 
connection. 
Of the Vertebral Column.—The vertebral column is divisible, in all the Marsupiata, 
into the usual classes of cervical, costal, lumbar, sacral and caudal vertebrae. The 
cervical vertebre invariably present the usual number, seven, and the usual character 
of the perforation of the transverse process, or rather the presence of both upper and 
lower transverse processes, and the union of their outer extremities with a rudimental 
rib. I found the cervical ribs distinct and unanchylosed in the dentata of a mature 
Perameles lagotis. Inthe Dasyures, Opossums, Perameles and Phalangers, the seventh 
cervical vertebra has only the upper transverse process, and consequently wants the 
character of the perforation, as in many of the ordinary Mammalia. In the Petaurists, 
Koala, Wombat, Potoroos and Kangaroos, the seventh vertebra is perforated like the 
rest; but in the Kangaroo both the dentata and atlas have the transverse processes 
srooved merely by the vertebral arteries ; and in the Koala and Wombat the atlas pre- 
sents only the perforation on each side of the superior arch. 
In Perameles and some other Marsupials, as the Cayopollin, an affinity to the Reptilia 
is manifested in the structure of the atlas, which exhibits a permanent separation of 
the superior lamine from the centre or body below. In the Koala and Wombat the 
body of the atlas remains permanently cartilaginous ; at least this is its condition in 
an adult skeleton of each of these animals in the Hunterian Museum, in which the 
lower part of the vertebral ring is completed by dried gristly substance. In the Petau- 
rists, Kangaroos and Potoroos, the atlas is completed below by an extension of ossifica- 
tion from the centres developed from the superior /amine into the cartilaginous nucleus 
representing the body ; and the ring of the vertebre is for a long time interrupted by 
a longitudinal fissure in the middle line, the breadth of which diminishes with age’. 
1 'This fissure is represented in figures of the atlas of a Potoroo and Kangaroo, given by Pander and D’Alton 
(Beutelthiere, fig. c. Pl. III. and VII.); but in some of the skeletons of these Marsupials examined by me, I find 
the ring completed and the fissure obliterated. 
