OF THE KOALA AND VULPINE PHALANGER. 559 



Trichosurus and Pseudochirns. The opening lies within the 

 hyoid ring about 5 mm, anterior to the beginning of the 

 oesophagus, so the naso-pharynx is exceedingly small. This is a 

 remnant of the condition present in the new-born animal. 

 Owen (11) describes how the larynx is gripped by the nasal tube 

 in the mammary foetus of the Kangaroo, and the milk stream is 

 divided by the larynx, which crosses the pharynx ; he gives 

 illustrations. 



Sections through the head and neck at difierent levels show 

 how the shape of the nasal tube alters from before backwards 

 (text-fig. 59, F and G). 



The Eustachian Tithee (text-fig. 59, h). — The lower orifices of 

 the tubes are slit-like, and lie on the infero-lateral aspects of the 

 nasal tube at a distance of 2*9 cm. posterior to the hard palate, 

 and at a point about 1 cm. posterior to the fauces. In Plate V. 

 pins are inserted into the inferior orifices of the Eustachian 

 tubes. 



Trichosurus vulpecula. 



The pharynx difiers from that of Fhascolarctos as follows : — 



1 . The tonsils are in the fauces. 



2. There is a ridge on the dorsal wall of the nasal tube, but 



none in the pharynx. 



3. The larynx crosses the pharynx and enters the nasal tube. 

 The nasal tube of Pseudochirus has a median doisal ridge 



(Plate Y., 0). 



The (Esophagus. 

 Phascolarctos cinereus. 



The cervical jt^ari (4*3 cm. long) is entirely concealed by the 

 larynx and trachea, and its mucosa is smooth throughout. The 

 thoracic part (7'8 cm. long) has, small longitudinal folds on its 

 inner surface. The abdominal pa^-t (1*8 cm.) is lined by mucosa 

 thrown into prominent longitudinal folds. At the point where 

 it emerges from the posterior surface of the liver it is in contact 

 dorsally with the right supra,renal capsule. 



Trichosurios vulpecula. 



The cesophagus projects beyond the left border of the trachea 

 in the neck, and it has a longer course ( = 3 cm.) in the abdomen 

 than has that of Phascolarctos. It is not in contact with the 

 right suprarenal capsule. In some examples its abdominal part 

 is much shorter, however. 



The Peritoneum. . 



Phascolarctos cineretis. 



The great omenttom is devoid of fat, but contains a well-marked 

 arterial arcade formed by a branch of the splenic ai'tery and a 

 Proc. Zool. Soc— 1921, No. XXXYIII. 38 



