OF THE KOALA AND VULPINE PHALANGEE. 571 



The anterior mesenteric artery describes a carve, convex 

 forwards and to the right, and terminates in the cfecum ; it 

 occupies the free edge of the c?ecal mesentery in the latter part 

 of its course. 



The branches supplying the lai'ge intestines arise from the 

 convexity of the curve, and those destined for the small intestines 

 are given off from the concavity. The highest branch anasto- 

 moses with the duodenal branches of the hepatic artery, and the 

 lowest one anastomoses in the pelvis with the hfemorrhoidal 

 vessels. The lowest branch to the ileum anastomoses with the 

 branches to the cjecum. 



The mesenteric areas between the branches of the mesenteric 

 artery contain rich networks of fine lymphatic vessels, and fine 

 branches of the solar plexus accompany the arteries. The 

 mesenteric veins have been figured already by Chalmers 

 Mitchell (9). 



In IVichosurus vuVpecula the cceliac axis arises separately. 



The Veins. 



The Anterior and Posterior Facial Veins have the usual forma- 

 tion, course, and tributaries. They unite to form the external 

 jugular vein on the surface of the exoccipital process. The latter 

 runs postero-mesially across the steiniomastoid to reach its lateral 

 border in the posterior sixth of the neck. It passes dorsal to 

 the posterior end of the sterno-mastoid and clavicle, and, anterior 

 to the neck of the first rib, it unites with the axillary vein to 

 form the precaval vein. Both veins are united by a long 

 V-shaped vena transversa. In Trichosurus vulpecula the vein is 

 more transverse (text-fig. 55 J. 



Tributaries. — Auriculo-tempoi-al, acronjial, ti-ansverse scapular, 

 muscular, ascending cervical and intei'ual jugular veins. These 

 vessels have the; usual distribution. No anterior jugular vein 

 is present. 



The v>ena transversa receives veins from the tongue, sub- 

 maxillary glands, and muscles of the raylo-hyoid region. 



At the point where the internal and external jugular veins 

 unite there are several small glands. 



The innomi^iate and precaval veins follow the usual course of 

 the Marsupial type, and the azygos veirts in my specimen are 

 similar to those described by Forbes (4). The intrathoracic part 

 of t\\e postcaval vein measures 1*5 em. 



The postcaval vein is formed in the usual manner, but the 

 only pai-t lying ventrally superficial to the abdominal aorta 

 crosses the termination of the latter. This arrangement is an 

 exception to Beddard's statement that " the Marsupials show a 

 very constant condition in that the postcava lies medianly 

 ventral to the aorta, so that on dissection the aoita is not seen, 

 being completely covered by the postcava " (21). 



It lies to the right side of the aorta, and close to it till it 



