134 



inner side of the ramus of the jaw, as in the same fossilg. In the 

 Thylacine and Ursine Dasyure, and in their fossil congeners, the 

 Thylacothere and 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 diet of the species. 



" In all those Marsupiata which have few or very small incisors, 

 the horizontal ?-anii 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 inter- 

 nal surface of the symphysis menti is almost horizontal, and is con- 

 vex from side to side in the interval between the molars and incisors. 

 The suture becomes obliterated in aged skulls ; it is also wholly ob- 

 literated 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 disjoined at the symphysis ; and in the Opossum, both the rami 

 of the lower jaw and all the bones of the face are remarkable for the 

 loose nature of their connection. 



" The vertebral column is divisible in all the Marsupiata into the 

 usual classes of cervical, costal, lumbar, sacral, and caudal vertebrae. 



" The cervical vertebrae invariably present the usual number, seven, 

 and the usual character of the perforation of the transverse process, 

 or rather the presence and union of the outer extremities of the 

 upper and lower transverse processes. In the Dasyures, Opossums, 

 Perameles, and Phalangers, the seventh cer\'ical vertebra has only the 

 upper transverse process, and consequently wants the character of 

 the perforation, as in many of the ordinary Mammalia. In the 

 Koala, Wombat, Potoroos, and Kangaroos, the seventh vertebra is 

 perforated like the rest ; but in the Kangaroo both the dentala and 

 atlas have the transverse processes grooved merely by the vertebral 

 arteries ; and in the Koala and Wombat the atlas presents only the 

 perforation on each side of the superior arch. 



" In the 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 laminae from 

 the centre or body below. In the Koala and Wombat the body of 

 the atlas remains permanently cartilaginous ; at least, this is its con- 

 dition 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 Petaurists, Kangaroos, and 

 Potoroos, the atlas is completed below by an extension of ossifica- 

 tion from the centres developed in the superior laminae into the car- 

 tilaginous nucleus representing the body ; and the ring of the ver- 

 tebrae is for a long time interrupted by a longitudinal fissure in the 

 middle line, the breadth of which diminishes with age. This fissure 

 is represented in figures of the atlas of a Potoroo and Kangaroo given 

 by Pander and d'Alton (Beutelthiere, fig. c. pis. iii. and vii.), but in 

 some of the skeletons of these Marsupials examined by me I find the 

 ring completed, and the fissure obliterated. In all the Marsupiata 

 the spine of the dentaUt is well developed botli in the vertical and 



