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Show 190t).] OX THE ENCEPHALIC ARTERIAL SYSTEM IN SAUROPSIDA. 59 and gave rise to " rosette-stages," about 2-5 fi to 3'5 /.i in diameter. A " rosette ' consisted of a schizont dividing up into merozoites. This parasite was probably the smallest Hsemogregarine yet described, and it occurred in large red blood-corpuscles, those of Triton cristatus being about 30^ in long diameter. The research on this parasite and allied forms was being continued. The following papers were read :- 1. A Contribution to the Knowledge of the Encephalic Arterial System in Sauropsida. By F r a n k E. B ed d a rd , M .A ., F.R.S., Prosector to the Society. [Received March 29, 1905.] (Text-figures 16-21.) The following pages contain some facts relating to the principal vessels of the arterial system of the brain in a number of Lizards, in a Python, and in the giant Tortoise, Testudo vicina. Some of these have not been hitherto studied; some have been examined by Rathke and others, and references to these anatomists will be found in the proper place. Most of the brains which I describe are now in the Museum of the Royal College of Surgeons. My principal object has been, next to the recording of new facts, to ascertain how far the characters offered by the distribution of these vessels, which are undoubtedly of use in the systematic arrangement of mammals, are also of use in the remaining Vertebrata for a like purpose. § Bra in of Varan us exantliematicus. Although the cerebral arterial system of Varanus griseus has been described by Corti *, 1 have a few notes to add to his description and comparisons to make with the other genera treated of in the present communication. The two vertebral veins are strong and mark the posterior end of the medulla, precisely as is the case with Iguana. The posterior pair of cerebellar arteries arise, as in Iguana, from the basilar artery at the middle of the medulla, and are larger than the anterior pair, which arise from the fork of the basilar in front. This fork is not quite so symmetrical as in Iguana. The left side and the left carotid are rather thicker than the right, and there is thus a suggestion of the marked inequality of these arteries in Python. The branches to the corpora bigemina and to the rest of the brain are quite as in Iguana; but the large size of the ophthalmic arteries is a point of likeness to Python. * De systemate vasorum Psammosauri grisei. 1853. |