SKELETON OF MARSUPIALIA. 



331 



213 



the Wombat to seven, fig. 213 ; but if we regard those vertebrae 

 only as sacral which join the ossa innominata, then there are but 

 four. In the Phalangers there are generally two such sacral 

 vertebra3, but in the Phalangista Cookii the last lumbar assumes 

 the character of the sacral vertebras both by anchylosis and partial 

 junction with the ossa innominata. 



In the Kangaroos and Potoroos the impetus of the powerful 

 hinder extremities is transferred to two anchylosed vertebrae. In 

 the Perameles there is only a 

 single sacral vertebra, the spine 

 of which is shorter and thicker 

 than those of the lumbar verte- 

 brae, and is turned in the con- 

 trary direction, viz. backward. 



In the Myrmecobius there are 

 four sacral vertebra by anchy- 

 losis, two of which join the ilia. 

 In Mange's Dasyure, two sacral 

 vertebrae are anchylosed, but it 

 is to the expanded transverse pro- 

 cesses of the anterior one only 

 that the ossa innominata are 

 joined. The same kind of union 

 exists in the Viverrine Dasyure, 

 but three vertebrae are anchy- 

 losed together in this species. In 

 the Phalangers and Petaurists 



there are two sacral vertebras. In Petaurus macrurus three are 

 anchylosed together, though only two join the ilium. In the Wom- 

 bat, fig. 213, the transverse processes of the numerous anchylosed 

 vertebra are remarkable for their leno^th and flatness : those of the 

 first four are directed outward and are confluent at their extremi- 

 ties ; the remaining ones are turned in a slight degree backward, 

 coalesce, and very nearly reach the tuberosities of the ischia: 

 behind these they gradually diminish in size and disappear in 

 the three last caudal vertebrae. The transition from the sacral 

 to the caudal vertebrae is here very obscure. If we limit the 

 sacral to the three or four which join the ilium, then there 

 remain twelve vertebra? for the tail. The spinal canal is com- 

 plete in all but the last three, which consist only of the body. 

 There are no haemal spines, and as only the six posterior ver- 

 tebrae, which progressively diminish in length, extend beyond 

 the posterior aperture of the pelvis, the tail is scarcely visible 



Pelvis of the "Wombat. 



