1904.] ANATOMY OF CERTAIN SHAKES, 119 



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 jacvlus, 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 

 aortse. 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 conicits the azygos, after a break, 

 reappeared in the region of the liver, where its course is shown in 

 the accompanjdng drawing (text-fig. 23, p. 118). It will thei-e 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 oflf branches on the one hand 

 to. the dorsal parietes, and on the other to the portal vein. 

 Antei'iorly to the liver the branches go to the oesophagus. In Eryx 

 jacvlus (text-fig. 20, p. 110, C.v.l., C.v.r.) there were conspicuous 

 traces of both posteiior cardinals behind the liver. As will be 

 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 arteiy 

 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, difier 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 difierences, 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 co7iicus 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). 



