336 



are numbered on coloured labels according to the TABLE OF SYNONYMS. The posterior 

 angles of the basisphenoid are produced backwards, and the carotid enters between this angle 

 and the alisphenoid bulla, and pierces the basisphenoid obliquely : the internal apertures are 

 separated by a space equal to both their diameters, and open on the posterior third of the 

 basisphenoid, which rises anterior to them to form the chiasmal platform. 



Presented by Sir Everard Home, Bart., V.P.R.S. 



1847. The atlas, axis, and third cervical vertebra of a Koala (Phascolarctosfuscus). 



The body of the atlas is anchylosed, as the odontoid process, to the axis ; the hypapo- 

 physis is not ossified ; part of its dried ligamentous remains are preserved. Ossification has 

 extended from the neurapophyses into the under part of the capsule of the primitive noto- 

 chord, and this part of the atlas developes a low tubercle on each side, representing the par- 

 apophysis. The diapophysis is short, broad, depressed, with a constricted base. The ver- 

 tebral artery has notched both the hind and the fore part of this base, in winding round to 

 perforate the neural arch above the anterior articular cavity. The parapophysis and diapo- 

 physis of the two succeeding vertebrae being united by a coalesced rudimental rib, present the 

 usual perforated character. 



Presented by Sir Everard Home, Bart., V.P.R.S. 



1848. The left humerus of the Koala (Phascolarctosfuscus). 



The deltoid ridge extends along its proximal half. The long and broad supinator ridge 

 terminates above in an unciform process ; the inner condyle is widely perforated : the olecranal 

 depression is very feebly marked. ( 



Presented by Sir Everard Home, Bart., V.P.R.S. 



Genus Petaurus. 



1849. The skeleton of the Long-tailed Petaurist (Petaurus macrourus). 



The inner condyle of the humerus is perforated. The ribs are thicker and broader than 

 usual. The 7 cervical vertebrae have their transverse processes all perforated on the left side, 

 but on the right the last is only notched : 12 vertebrae are dorsal, 7 are lumbar, 3 are sacral, 

 and 26 are caudal : of these only the fifth, sixth and seventh have small rudiments of haem- 



apophyses. 



Mm. Brookes. 



1850. The skeleton of the Sciurine Petaurist, or Flying Opossum (Petaurus sciurceus). 



The inner condyle of the humerus is not perforated. The marsupial bones are wanting in 

 this skeleton. There are 7 cervical vertebrae, and the transverse process of the sixth is first 

 pierced by the vertebral artery. The dorsal vertebras are 12 in number, the lumbar 7, the 

 sacral 2, the caudal 19 : in these the haemapophyses, if present, have not been preserved. 



The species of the genus Petaurus are limited to Australia, and closely resemble, or are 

 identical with, the true Phalangers in their dental characters and the structure of the feet. 



