550 



DE. C. F. SONNTAG ON THE COMPARATIVE ANATOMY 



musclfts are not so powerful. 4. The vena transversa is horizontal, 

 and runs between the anterior facial veins. It is coiniected to 

 the internal jugular veins (x) and receives two submental veins ; 

 a small part of it loops into the interramal space. '5. The 

 sterno-hyoid muscles are attached to the hyoid bone. 6. The 

 superficial sheet between the sternomastoids of Phascolarctos 

 is absent. Neither in Phascolarctos nor in Trichosuj^iis does the 

 vena transversa receive laryngeal veins. 



Text-figure 55. 



The superficial anat-omj' of the neck of Trichosurus vulpecula. 

 Numbers as in previous figure. 



The deep anatomy of the neck differs greatly in the two 

 species : — 



Phascolarctos cinereus. 



When the muscular sheet described above is removed the 

 conditions shown in text-fig. 56 make their appearance. 



The walls of the mouth (/) and pharynx (g) lie immediately 

 under cover of the muscular sheet, and the following structures 

 are seen to lie on their externa*! surface : — 



1. Two long, nari-ow strap-like genio-hyoid muscles (a, a) 

 running from the symphysis menti to be attached to the hyoid 

 bone (m) and larynx (I). They cross the lingual arteries (c). 

 2. The lingual arteries. 3. The hypoglossal nerves (d). 4. The 

 pharyngeal branches of the vagi (e), which are very tortuous. 



