REPORT ON THE MARSUPIALIA. 155 



take origin, but the short wide trunk divides differently ; it first gives off the left 

 common carotid artery, and then proceeding onwards for a short distance, divides (like 

 the innominate in man) into a right subclavian, and a right common carotid. 



Considerable variation, therefore, is exhibited by Marsupials in the mode of origin of 

 the carotid and right subclavian trunks. The separate origin of the left subclavian is 

 almost universal throughout the group. Mr. Forbes, Prosector to the Zoological Gardens 

 in London, mentions one member of the order (viz., Belideus breviceps*) in which all 

 the vessels arise from one common trunk or anterior aorta. 



The coronary arteries in all the specimens were two in number, and in all the left 

 was much larger than the right. Their openings in the aorta were distinctly above the 

 level of the free margins of the valve segments. 



In the Thylacine and Dasyure the superior intercostal artery of each side springs directly 

 from the aorta at the point where it first touches the spine. This vessel lies in series with 

 the other intercostal arteries, but differs from them in being about three times as large. 

 It runs forwards, and after supplying twigs to the three anterior intercostal spaces it dis- 

 appears by passing upwards to the dorsal region between necks of the third and fourth 

 ribs. Gaining the superior aspect of the vertebral column, it proceeds forwards between 

 the splenius and semi-spinalis muscles. It can be traced as far as the occipital region." 



Pulmonary artery. 



The only point to be noted in connection with this vessel is that in none of the 

 animals examined by me was there the slightest vestige of an obliterated ductus arteriosus 

 to be discovered. 



Great veins of the heart. 



As usual in Marsupials each animal possesses three great caval veins, viz. — (1) a 

 right anterior vena cava, (2) a left anterior vena cava, and (3) a posterior vena cava. 3 



The right anterior vena cava has the same position, relations, and manner of ending 

 as the superior vena cava in man. It pierces the pericardium on the inferior aspect of the 

 root of the right lung and opens into the anterior part of the right auricle. 



The left anterior vena cava retains its embryonic course and, piercing the pericardium 

 un the inferior aspect of the root of the left lung, it turns to the right, on the posterior 

 aspect of the heart, in the auriculo-ventricular groove. Here it occupies the same position 



1 Mr. W. A. Forbes, on the Koala, Proc. Zool. Soc, January 1881, p. 189. 



2 In Professor Owen's celebrated article on the Marsupialia in the Cyclopaedia of Anatomy and Physiology, the 

 author states that the brachial artery in Thylacinus passes over the internal condyle of the humerus, impressing it 

 with a more or less deep groove. In both of my specimens the artery along with its accompanying veins passed 

 tlrrough the supra-condyloid foramen. 



3 In the Belideus breviceps there appears to be only one anterior vena cava. Vide Mr. Forbes' paper on the Koala, 

 Proc. Zool. Soc, 1881, p. 188. 



