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Show 5 0 4 MR. F. E. BEDDARD ON THE VASCULAR AND [May 1, enters a distinct foramen larger than itself, formed in the tendons exactly in the middle line. Before entering this foramen it gives off a slender branch to the oesophagus. The intercostal artery can then be plainly seen to divide into two. Erythrolamprus has only one gastric artery proper. This arises from the aorta about on a level with the posterior end of the liver *. The following superior mesenteric artery arises from the aorta about on a level with the gall-bladder. It sends off, of course, a gastric branch. The number of gastric arteries varies much among Snakes t, and it is therefore of importance to record the fact, though its systematic value is not yet apparent. The azygos vein of Erythrolamprus is in some ways remarkable as compared with that of other serpents. For it is particularly short though its branches are of considerable calibre. There are, in fact, only three branches, supplying as many intercostal spaces, which unite to form the single azygos trunk. This lies on the right side of the body, and of course joins the anterior vertebral vein before the latter enters the heart. This is apparently shorter than the azygos of any snake yet described. The azygos of Coronella getula is just larger-four interspaces. In Coluber corais the single azygos vein also lies on the right side of the body. It is, however, a little more extensive though perhaps slighter. It supplies six intercostal spaces. It is to be noticed that in both these Colubrines the azygos vein is of very limited extent as compared with the Pythonine and Boine Snakes, speaking generally, for Eunectes is an exception. This fact is in correspondence with the generally limited development of superficial parietal veins in non-Boine Snakes as compared with the Boidfe. Even in Eryx, though a genus containing small-sized species, the azygos is, as I have pointed out+, comparatively long. I may take this opportunity of pointing out that in Python regius -a small Python-the azygos extends over about 15 vertebrae, to 2 inches or so behind the heart. The vena cava inferior of Coluber corais shows an interesting vestige of the umbilical vein. Near to the anterior end of the liver the vena cava has a short diverticulum, which seems hardly to be pervious, lying to the left side and extending obliquely backwards. I take it that this seam is the equivalent of the thick branch of the same vein in the same position which I have described in Python sebce §, and which I then regarded, and still regard, as a last remaining fragment of the embryonic umbilical. It is clearly even more rudimentary in the present species. * I talce this opportunity of noting that in Erythrolamprus cesculapii there is a detached fragment of the liver lying upon the post-caval vein about an inch behind the extremity of the liver. This is quite analogous to the division of the pancreas and of the spleen which is to be seen in other Snakes. It is also to be compared to the extremely thin posterior end of the liver in Corallus (vide infra, p. 518) In these cases the gland appears to be in course of reduction in length. It is possible that this is connected with a shortening of the body generally which has conspicuously taken place in certain Vipers. t Beddard, " Circulatory System in OphidiaP. Z. S. 1904, vol. i r, 331 % P- Z. S. 1904, vol. ii. p. 119. § p. z. S. 1906, vol. i. p. 28. |
