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Show 188 MR. W. A. FORBES ON THE KOALA. [Jan. 1 8, in one of my specimens, three columna? carnea?, which also decrease in size from right to left. On the side corresponding with the septum the valve is attached, not to a columna carnea, but by chorda? tendinea? inserted on the septal wall. There is apparently only a single opening for the coronary veins, just at the entrance of the inferior cava into the auricle. The aorta gives off, in the specimen which died in the Society's Gardens, three vessels from a common trunk, and then the left subclavian, as in Phalangista and most other Marsupials1. In another specimen, however, the arrangement is as in Man and as in Phascolomys, the left carotid arising independently from the aortic arch. Of the two vena? azygos, each opening into the superior cava of its side, the left is much the larger, the right being formed mainly by vessels derived from only the first few intercostal spaces, whilst below these the veins of the right side pass over, behind the aorta, into the left azygos. This is an arrangement I have found in several Marsupials examined, including Phascolomys, Belideus, Cuscus, and Phalangista, though not in Petrogale or Hypsiprymnus. In Phascolomys there exists a commissural branch between the first intercostal vein on the right side going to the left, and the last going to the right, vena azygos. In the Hedgehog, and some other animals according to Prof. Owen (Anat. Vert. iii. p. 553), the right is also smaller than the left azyyos, though usually the reverse condition holds ; and in the highest forms, where there is only one vena azygos, it is the right that persists. The external and internal iliac arteries come off separately from the aorta, there being no common iliac arteries. This disposition is, I believe,nearly universal2 in the Marsupial?, but is by no means confined to them, as I have found it in Tamandua, Tapirus, and Hyomoschus, and Prof. Watson records it in LLycena crocuta (P. Z. S. 1879, p. 89). The lungs are simple in form. The right side has three, the left two lobes; the lower lobes of each side being about equal in size, and much larger than the others-half as big again as the upper, or two upper, lobes. There is no azygos lobe at all. The female generative organs of Phascolarctos have not been, so far as I have been able to ascertain, hitherto described, though Mr. A. H . Young has lately given us an excellent account, with figures, of the corresponding system in the male. In their essential points they differ in no important respect from those of the Wombat3. 1 P.S. Feb. 11, 1881. In a fresh specimen of Belideus breviceps, which I have just dissected, I find only one trunk arising from the aortic arch; this splits up into 3 branches-a left innominate, dividing into the subclavian and carotid branches for that side, a right carotid, and a right subclavian. Moreover, as in no other Marsupial known to me, there is only one anterior c w a , the right and left innominate veins joining to form a larger trunk, some ^ inch long, which opens into the auricle. 2 In a Cuscus maculatus that I dissected I found the abdominal aorta splitting up into four trunks, the right and left external, and the right internal iliacs, whilst from the remaining or median (caudal) one, the left internal iliac was given off some way below the level of the other. 3 For description of these see Owen, P. Z. S. 1836, p. 52, and Anat. Vert. iii. p. 680 et seq. |