OP THE KOALA AND VULPINE paALANGER. 



549 



by the clavicle (17) as in all Marsupials except the Peramelidse, 

 which have no clavicles. 



In the space between the mesial borclers of the sternomastoids 

 there is a thin muscular sheet formed by the mylo-hyoid (i) 

 anteriorly, the digastrics (9) antero-latei'ally, and the sterno- 

 hyoids (13) posteriorly ; the sterno-hyoids have become separated 

 from the hyoid bone in this specimen, but the whole sheet plays 

 over it. Anterior to the digasti'ics are the submaxillary glands (4). 



Text-figure 54. 

 I — /. 



The superficial anatomy of the neck of Fhascolarctos cinereus. 

 5 and 6. anterior and posterior facial veins ; 7,20. exoccipital process; 8. posterior 

 auricular vein; 11. external jugular vein; 16. supraclavicular nerves; 

 17. clavicles; 19. masseter. Other immhers in text. 



The space between the sheet and the sterno-mastoids is bridged 

 over by a triangular fascia (14) which covers the common carotid 

 artery, vago- sympathetic nerve-trunk, and the nerve to the 

 pretracheal muscles. It does not cover the internal jugular vein, 

 which is under cover of the sterno-mastoid. 



Trichosuras vulpecula (text-fig. 55). 



The superficial anatomy differs from that of Fhascolarctos in 

 the following respects : — 



1. The platysma is not so well developed. 2. The external 

 nasal artery does not follow a cheek-pouch. 3. The auricular 



