1905.] VASCULAR SYSTEM OF LACERTILIA. 487 



hcena are not joined by ductus Botalli to the systemic arch. 

 The left systemic arch in A. brasiliana is considerably largei' 

 than the right. 



The left anterior vei'tebral artery is not exposed for the whole 

 of its course within the body-cavity. Shortly after its origin 

 from the right aortic arch, and while its covirse is still oblique 

 and towards the left side of the body, it is covered by a muscular 

 layer, which is a continuation of the thick muscle covering the 

 vertebral centra in the cervical region, and forming a soft cushion 

 for the oesophagus to rest upon, and corresponding, I presume, to 

 the longus colli. This muscle (see text-fig. 69, p. 486), after 

 crossing the left anterior vertebral artery as already mentioned, 

 becomes more and more slender and disap)pears. It is important 

 to note that it is not symmetrical, and that no corresponding slip 

 covers the right anterior vertebral artery. This curvature of one 

 artery at least by a muscular slip seems to me to have a bearing 

 upon the homology of the arteries. 



The origin of these arteries from the right aortic arch, and the 

 fact that one springs from the aortic stem in front of the other, 

 is a distinct point of likeness to the subclavians of other Lizards, 

 which give off an anterioily running vertebral. The loss of the 

 fore limbs and the increased importance of the neck for burrow- 

 ing purposes might account for the disappearance of the main 

 subclavian stem and the increase of its vertebral branch. The 

 burrowing of the artery in question beneath the musculature to 

 which I have referred is found in the case of the subclavian of 

 Tillqua^ . 



There are three very slender msophageal arteries arising from 

 the aorta,. They are followed by three gastric ai"teries, of which 

 the last lies a little way behind the gall-bladder. The mesenteric 

 arteiies have been shown by Rathke t to differ considerably 

 among the Amphisbsenidee. In the species examined by me 

 there is a coeliac ai-tery followed by a common mesenteric ; the 

 intestine is also supplied by a posterior mesenteric which arises 

 from the aorta among the renal arteries. 



The spermatic arteries arise just after the arteria mesenterica 

 communis ; the right is slightly in advance of the left. They 

 both arise in common with an intercostal. On the left side an 

 additional spermatic ai-teiy arises very close behind the main 

 one. 



Behind the spermatic arteries a number of fine arteries sujjply 

 the vas deferens. Of these I counted six on the left side, and 

 thei'C are about as many on the right. As a rule (five on the left 

 side), these arteries arose directly from the aorta and indej^en- 

 dently of the intercostal arteries. 



The renal arteries differ in number on the two sides of the 

 body. I counted iowv on the left and five on the right side. 



* Beddard, P. Z. S. 1904, i. p. 465. 



t Abb. Ak. Wiss. Miuicbei), ix. (1863). See also Hocbstetter, Morpb. Jabrl). 

 xxvi. (1898). 



Proc. Zool. Soc— 1905, Vol. IT. No. XXXIII. 33 



