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Show 4 6 2 MR. F. E. BEDDARD ON THE [Nov. 28, Arterial System.-The arrangement of the aortic arches is precisely like that of the Lacertilia. It is not so different from that of Lacerta, Lguana, &c. as is the arrangement found in Varanus. The carotid arch gives off the usual three branches before joining posteriorly the aortic arch. The third branch, that to the muscles of the shoulder, arises just before the carotid arch joins the aorta. As to the systemic (aortic) arch (see text-fig. 59), it is interesting to note that on both sides this arch gives off an oesophageal artery; frequently, as is well known, the right arch alone gives off such a branch. Just at the meeting of the two aorta? the subclavians arise. A careful dissection shows (see text-fig. 59, Sci.) that both subclavians arise close to each other- and one a little in advance of the other-from the right aortic arch only just before it joins the left. Each subclavian gives off immediately after its origin a forwardly directed vertebral artery, which plunges at once into the parietes. Immediately after the junction of the two aortse arises the first pair of intercostals. Between this pair and the next arises a gastro-oesophageal artery. This artery is separated from the gastric by three pairs of intercostals, and five pairs of intercostals lie between the gastric and the superior mesenteric artery. The intestinal arteries 1 need not refer to, as they have been already treated of by Hochstetter *. It may be mentioned that, as in some other Lizards (e. g. Gerrhosaurus t), the pulmonary arch gives off on each side a branch which runs along the windpipe and sends off branches to the thyroid. Venous System.-There is no question that, apart from details, the venous system of Hatteria is distinctly Lacertilian. Nor do the differences which it shows from Lacertilia tend to prove a nearer- resemblance to the Chelonia or to the Crocodilia, On the other hand, I believe it possible to detect likenesses to the Opliidia. This, however, in my opinion, does not argue a special affinity between Hatteria and the Oplridra, but the antiquity of the Hatteria type, which pala?ontology, as is well known, has proved. The Lacertilia are distinguished by the double vena cava posterior, which is double, that is to say, as far forward as the gonads, from which point onwards there is but a single trunk formed by the fusion of the two trunks. As a rule, also, there is an asymmetry between the two vena? cava?, or eflerent renals as they are commonly termed. When there is this difference the right vessel is of greater calibre than the left. In Hatteria we meet with the same conditions, and here the left vena cava, is of distinctly less calibre than the right. The two vessels, moreover, * Morph. Jahrb. vol. xxvi. p. 217. % 3 7 ,ep aid' " Anatomy of Gerrhosaurus," P. Z. S. 1905, vol. ii. p. 263, text- |