| OCR Text |
Show 1 9 0 4 .] ANATOMY OF CERTAIN SNAKES. 1 1 9 of its side. This vessel appears to be well developed in some Boid serpents, and that fact appears to me to indicate the retention of a primitive feature*. In Eryx jaculus, for example, the vein, which is on the right side, extends back over no less than twelve intercostal spaces and nearly reaches the junction of the two aortee. This contrasts with the same vein in Coronella getula, which only extends over four of these spaces. In a specimen of Eryx conicus the azygos vein extended only over ten vertebrae. In both specimens of Eryx conicus the azygos, after a break, reappeared in the region of the liver, where its course is shown in the accompanying drawing (text-fig. 23, p. 118). It will there be seen that the vertebral vein with one gap near the anterior end of the liver runs continuously to a point some little distance behind the liver. It gives off branches on the one hand to the dorsal parietes, and on the other to the portal vein. Anteriorly to the liver the branches go to the oesophagus. In Eryx jaculus (text-fig. 20, p. 110, C.v.l., C.v.r.) there were conspicuous traces of both posterior cardinals behind the liver. As will bt seen in the drawing referred to, the left posterior cardinal is continued anteriorly beyond its junction by a conspicuous branch with the portal trunk in the immediate neighbourhood of the liver; posteriorly it ends near to the commencement of the right-hand vein, the two being therefore supplementary to each other. The left is considerably the longer. The right extends back a little way beyond the origin of the superior mesenteric artery from the aorta. In Python sebce a corresponding vein occurs in the region of the liver, but it extends both further forward and backward than I have observed in Eryx. Anteriorly it extends beyond the junction of the two aortse, and posteriorly it reaches very nearly to the gall-bladder. I do not for the present suggest that these longitudinal vessels are more developed in the Boidse. I simply call attention to their arrangement. § On the Specific Differences between Eryx jaculus, E. johni, and E. conicus. These species can be readily separated by external characters, as Boulenger plainly sets forth in the British Museum ‘ Catalogue of Snakes.' They also, however, differ in other points besides the obtuse or pointed tail, the absent or present mental groove, and the form of the rostral scale, &c. There are differences, in the first place, in the form of the liver. In Eryx jaculus and E. johni the lobes are unequal, and the right lobe extends further down the body than the left, to the extent of about half an inch. In Eryx conicus they are as near as possible exactly equal. As these results depend upon the examination of two examples of each of the species E. jaculus and * As I have pointed out in a preliminary account of some of the facts detailed in the present communication (Ann. & Mag. Nat. Hist. (7) xiii. p. 233). |
