MARSUPIALIA. 



Fie,. 134. 



"09 

 



Branches of tha abdomhtal aorta, Kangaroo* 



receives also the coronary vein of the heart: 

 the termination of this and the two other venous 

 trunks in the right auricle has already been 

 noticed. 



Respiratory organs. In the condition and 

 structure of the respiratory organs all the Mar- 

 supial species adhere to the Mammalian type ; 

 the only tendency to the Ovipara is in the 

 entireness of the tracheal rings in certain spe- 

 cies. In the Phalangista fiitiginosa, where I 

 counted twenty-nine rings, the first four-and- 

 twenty were entire ; below these they were 

 divided posteriorly, the interspace growing 

 wider to the twenty-ninth ring. In the Dasi/- 

 wus macrurus the rings of the trachea are 

 twenty-three in number, and are incomplete or 

 rather ununited behind. In the Perumeles the 

 tracheal rings are divided posteriorly by a fis- 

 sure. In no species have I found the trachea 

 divided near the larynx into two long bronehise, 



as in the Rodent genus IJcLitni/s, nor convo- 

 luted in the chest as in the Edentate Sloth, both 

 of which modifications are more striking ap- 

 proximations to the oviparous type of structure 

 than the entire rings above-mentioned. 



The lungs present the most simple form in 

 the Wombat, in which they consist of a single 

 lobe on both the right and left sides, with a 

 small lobulus azygos extending from the right 

 lung to the interspace between the heart and 

 diaphragm. 



In the Macropus major I found the right 

 lung with two notches on the anterior margin, 

 and the left lung undivided. In the Macropus 

 Parryi both lungs had one or two notches. 

 In another Kangaroo I found the right lung 

 divided into four lobes, the left into two. Tte 

 azygos lobe is large in consequence of the 

 length of the chest in the Kangaroos, and the 

 distance of the heart from the diaphragm : it is 



