In an interesting recent paper, Kapoor et al. 2003* Show the Circle of Willis in several different species. Their key is either absent or well hidden. This may help!

1. Rostral/anterior cerebral artery.
2. Internal carotid artery.
3. Rostral/anterior communicating artery.
4. Caudal/posterior communicating artery.
5. Caudal/posterior cerebral artery.
6. Basilar artery.
7. Median anterior artery.
8. Anterior cerebellar artery.

NB., If the authors read this and feel I am in error. Sorry! Please just email me and I'll correct it!

Anatomia, Histologia, Embryologia
Volume 32 Issue 6 Page 347 - December 2003
Morphology and Comparative Anatomy of Circulus Arteriosus Cerebri in Mammals K. Kapoor, V. K. Kak and B. Singh