Proceedings of the general meetings for scientific business of the Zoological Society of London, 1904 vol. 2

Page 145

120 ON THE ANATOMY OF CERTAIN SNAKES. [May 17, E. conicus, the character may, I take it, be regarded as a genuine, if small, difference. Secondly, the right lobe of the lung extends further back in Eryx jaculus and E. johni. In those species it reaches the gall­bladder ; in Eryx conicus it falls short of the gall-bladder by at least an inch. The superior mesenteric artery arises in Eryx jaculus and E. johni distinctly in front of the gall-bladder. In Eryx conicus its point of origin is as distinctly behind the gall-bladder. This character is perhaps less likely than some others to prove of value as an absolute mark of distinction. More important are other differences in the vascular system. In Eryx jaculus, though it is the smaller species, there are appa­rently, as a rule, two arteries supplying each kidney ; in Eryx conicus there is but one to each kidney: and here apparently E. johni agrees with E. conicus. The intercostal arteries have a different arrangement in the two species. In E. jaculus there is a well-developed posterior vertebral artery formed by the junction of irregularly arising intercostals ; in E. conicus this does not exist (except as the merest rudiment). The paired intercostals com­mence further forward in E. jaculus than in E. conicus. E. johni in these particulars is somewhat intermediate. In E. jaculus there is a double connection of the anterior abdominal vein with the afferent renals posteriorly; in E. conicus this occurs only on one side. E. johni agrees with E. jaculus. In relation to these anatomical differences, which appear to me to be fully as great as those which distinguish either species from Eunectes, I Avould draw attention to the restricted range of E. conicus and to the wider distribution of E. jaculus and E. johni. Resume of principal facts. It may be convenient to deduce from the foregoing pages the main facts in the vascular system of the Boidse examined ; such may be divided into two heads, i. e., those which appear to argue a basal position among the Opliidia, and those which are of sys­tematic importance in the group. As to the former it may be noted that (1) The heart is always without the least trace of a guber-naculum cordis. (2) The two aortse are usually equisized at their point of union to form the dorsal aorta. (3) The renal and gastric arteries are much fewer in number than in other Ophidia, the former consisting generally of only one artery to each kidney. This distribution has no relation to the size of the kidney. (4) The intercostal arteries are always symmetrical and for the most part regular in then- arrangement, frequently in regular pairs.