1905.] ARTERIES OF THE BRAIX IK BIRDS. Ill 



bends inwards and runs in a course which is exactly parallel to 

 the anterior cerebral artery. 



Gathartes atratus. — The brain arteries of this New- World 

 Vulture difier from those of the Old-Woi-ld Falconidse described 

 above in a variety of points. In the first place, the anterior 

 spinal artery is single and joins the basilar with the merest trace 

 of asymmetry Anteriorly the basilar divides into two branches, 

 of which that going to the left carotid is rather the larger. 

 Anteriorly, again, the carotid div^ides into the ophthalmic and tlie 

 common trunk of the middle and anterior cei'ebrals. In Aquila 

 and Fcdco the anterior cerebrals do not arise in this way, but 

 separately and anteriorly from the ophthalmics, as is the case 

 with many other birds also. The middle cerebrals do not curve 

 round to meet each other towards the middle line, but run 

 straight forward in a way much more characteristic of the 

 Cranes. 



Psophia leuGoptera. — I have examined two brains of this species 

 which show an absolute agreement in all characters of importance, 

 and indeed only one point of difi'erence that I was able to detect. 

 This concerns the junction of the anterior vertebral artery with 

 the basilar at the point where the latter is formed by the con- 

 vergence and union of the cerebellar arteries. One specimen was 

 very nearly symmetrical in this region, the other less so. In the 

 former, the anterior spinal artery communicates with the basilar 

 only partly and indirectly by way of the left cerebellar. In the 

 second specimen, the point of opening of the anterior spinal was also 

 into the left cerebellar, but further away from the point of union 

 of the two cerebellar arteries. Posteriorly, as in Anthropoides 

 paradisea and some other birds, the anterior spinal artery is 

 double. I only observed this in one specimen, but should not 

 like to record it as a variation, since the apparent difference may 

 be merely a question of deficient injection. In both specimens 

 the circle of Willis is, as in so many other birds, asymmetrical. 

 The basilar arteiy is, in fact, connected only with the right 

 carotid, as is the case with Anthropoides paradisea. Just before 

 joining it the basilar gives off the artery to the corpus bigeminum 

 of its own side. The middle cerebral artery curves round, as in 

 the Birds of Prey, towards the middle ventral line of the brain 

 to the extremely rudimentary olfactory lobes, nearly meeting its 

 fellow. In this feature Psophia distinctly differs from AiUhro- 

 poides paradisea. The anterior cerebral arteries arise about 

 halfway between the origin of the middle cerebrals and the middle 

 line of the brain. They are slender and not conspicuous. 



Tantalus ibis, — The brain of this bird (text-fig. 19, p. 112) which 

 I examined is particularly well injected, and shows apparently all 

 the small arteries as well as the larger ones. The anterior spinal 

 artery (text-fig. \^,A.sp.) is double for a portion of its course, but 



