30 MR. F. E. BEDDARD ON THE [Jan. 16, 



noted, therefore, that Python differs from Eunectes in that the 

 anterior abdominal of the latter remains double for some distance 

 forwards after its origin, while in Python the roots join at once to 

 separate and rejoin later. 



Azygos Vein. — As in Eimectes, the azygos vein of Python sebce 

 is retained upon the right side only, but it is less extensive in the 

 former than in the latter snake. The azygos vein just before it 

 enters the right heart receives a stout branch running up vei'ti- 

 cally from the parietes and a thinner branch coming from the 

 neck-region. Posteriorly the vein passes backwards, and soon 

 divides into two trunks which are thin. The more dorsal of 

 these runs close to the body-wall and receives twigs from each 

 intercostal space. The upper bi-anch luns in close connection, or 

 rather contact, with the lung, for it does not appear to receive 

 any branches fi'om that viscus. After the tei-mination on the 

 parietes of the lower branch of the azygos, this upper bi'anch 

 bends down and supplies, or rather receives, blood from the inter- 

 costal spaces some way down the body, though not so far as the 

 region of the hepatic parietal vessels, wiiich will be dealt with 

 immediately. It takes up blood from the next intercostal space 

 to that which furnishes the last branch to the lower of the main 

 branches of the azygos. There is thus no break in the cii-culation 

 of this region of the body. 



Vessels of Neck. — Although the facts concei-ning the vessels of 

 the neck have been made known by Jacquart, 1 may take this 

 opportunity of pointing out that in their disj^osition there is an 

 obvious difference from the corresponding vessels of Eunectes. In 

 the latter snake all the four typical vessels are present *, viz., 

 two running along the trachea, and two anteiioi- vertebrals ; 

 whereas in Python (at least in P. sebce) there are only three 

 of these main venous trunks present, the left vertebral being 

 absent. There is also a disproportion between the two tracheal 

 or jugular trunks, the left being very much smaller in Python. 

 I did not observe such a difference in Eunectes. This series of 

 facts shows that it is not possible to place the two genera of 

 Boidte in ascending relations to each other in respect of the 

 venous system ;. for while Eunectes is more primitive in the 

 arrangement of the main veins of the neck, this genus is less 

 primitive in the fact that the anterior abdominal has only one 

 posterior connection with the veins of the posterior region of the 

 body, whereas both are present in Python. 



Hefatic Portal Veins. — These veins are constituted in Python 

 sebce upon the plan which is to be found in Eunectes and Eryx. 

 In all of these genera the parietal system {i. e. longitudinal veins 

 running along the parietes and collecting the blood from the 

 several intercostal branches before rendering it up to the liver 

 circulation) is much developed. There are, however, differences 

 in the way in which this system is formed in these various Boine 



* Oulj' three are figured by Gadow in Boa madagascariensis (loc. cit. pi. cxxxv.). 



