154 



THE VOYAGE OF H.M.S. CHALLENGER. 



by Professor Owen, in his great work upon Comparative Anatomy, in the heart of the 

 Kangaroo and of the Wombat (p. 518, figs. 401 and 402, a.a). 



Aorta, 



In all the animals examined, the aorta describes a very perfect and uniform curve 

 over the root of the left lung. It reaches the spine opposite the lower border of the fourth 

 dorsal vertebra, and then turns backwards. 



Except in the case of the Thylacine and Phascogale, the other animals differ con- 

 siderably in the manner in which the great vessels arise from the summit of the aortic 

 arch. They all agree, however, in so far that the left subclavian artery has a separate 

 and independent origin from the aortic arch before it turns upwards and backwards to 



Fig. 4. — Aortic Arch in Thylacine, Dasyurns, Cuscus, and Vulpine jihalanger. 

 li.S. Right subclavian. L.C. Left common carotid. 



K.C. Right common carotid. 



L.S. Left subclavian. 



$.1. Superior intercostal. 



reach the spine. In Thylacine and Phascogale, the other vessels spring by a short wide 

 trunk from the arch. This very soon gives off the right subclavian artery, and then, 

 continuing forwards for some distance upon the trachea, it finally divides into the two 

 common carotid arteries. In the Dasyure the two subclavian arteries come off separ- 

 ately and between them a trunk takes origin, which, after passing forwards upon the 

 trachea for nearly an inch, divides into the two carotids. In the Dasyurus macrurus, 

 the great vessels of the aortic arch come off in the same manner as in the Thylacine. 1 

 In the Cuscus two vessels proceed from the summit of the aortic arch, viz., the left 

 subclavian and a short wide trunk which very soon breaks up into the two common 

 carotids and the right subclavian. In the Vxdpine phalanger the same primary vessels 



Professor Owen, Notes of a Dissection of a Long-tailed Dasyurus,¥ioc. Zool. Soc., 1835, p. 7. 



