ED E NT A TA. 



59 



Iq the Marsupialia, the number of thoracico-lumbar 

 vertebrse is invariably 19, although there are some apparent 

 exceptions, in which the last lumbar assumes the form of a 

 sacral vertebra. The rib-bearing vertebrse are always 13, 

 except in the Koala {Phascolarctos)^ which has but 11, 

 and one species of Wombat ^Phascolomys vonibatiis\ whicli 

 has 15. The Hairy-nosed Wombat {P. latifrons) has the 

 ordinary number. 



In the Kangaroos, the lumbar vertebrae have largely 

 developed metapophyses and an apophyses, and moderate- 

 sized transverse processes much curved forwards. 



In the running and jumping Bandicoots {Perameles) the 

 lumbar vertebrae have very slender, long, forward-directed 

 spines, and long transverse processes. In the climbing 

 Opossums {Dide/p/iys), on the other hand, the spines are 

 very short and broad from before backwards. 



The MoNOTREMATA agree with the Marsupials in the total 

 number of trunk vertebrse, but those that bear ribs are more 

 numerous, viz. 16 in Echidna, and 17 in Ornithoiiiyiiclms. 



The spinous and transverse processes are very short, and 

 the ribs have no articulation with the latter, but are 

 attached to the bodies only, the greater part of the articular 

 surface being below the neuro-central suture, the reverse of 

 what occurs in the higher Mammals. In the thoracic ver- 

 tebrae the canals for the exit of the spinal nerves perforate 

 the neural arch. 



