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Show 702 MR. GERARD W. BUTLER ON THE [Nov. 19, organs (oesophagus, and aortic roots, &c), explain the deceptive position of the rudimentary left lung. Only one or two Snakes among those which I have examined are so deceptive as Heterodon platyrhinus, in the matter of the situation of tbe rudimentary lung, and none more so; and thus, having explained this case, I need not, I think, discuss any others, since all those that have come under m y notice can be explained in the same way. I give, however, a few other figures [figs. 5-9] of sections through different Snakes to show the kind of displacement of the viscera one finds, and to show how what is morphologically the median plane is indicated by the blood-vessels. On referring to the figures we note that the characteristic displacements are-(1) of the right lung from the right side into a dorsal position underlying the vertebral column and extending more or less into the left half of the body, and, corresponding to this, displacements (2) of the oesophagus along the left side ventral-wards, (3) of the aorta to the left side, and (4) of the liver towards the right side. IV. ON THE COMPLETE OR PARTIAL SUPPRESSION OP THE EIGHT L U N G IN AMPHISBAENIDAE. A reference to the list on p. 706 (which includes species of the genera of Amphisbcenidce in the British Museum Catalogue, with the exception of the rare forms Chirotes, Rhineuret, and Agameclon) shows that with the exception of Trogonophis wiegmanni, and to a lesser extent of Pachycalamus brevis, the right lung is rudimentary or absent altogether in all the Amphisbaenidae examined, while in these two it is distinctly smaller than the left. So far, then, as m y observations go, this would seem to be a characteristic peculiarity of the Amphisbaenidae. As to Chirotes1 two writers 2 have made themselves responsible for the statement that the right lung is much larger than the left; while a third 3 has given a figure of the lungs apart from the other organs, in which the larger lung is called the right. This evidence would at first sight seem to settle the matter, and of course it is quite possible that the published view is correct. As Chirotes differs markedly from the other Amphisbaenidae in its possession of fore limbs, why, it may be said, should it not differ in respect of its lungs ? Nevertheless, if, as seems indicated by its outward appearance, and as appears to be agreed by those who have studied its anatomy, Chirotes is an Amphisbaenid, there is a certain pre- 1 For a preliminary notice of a division of these animals into three genera, see Cope, " O n the Genera and Species of Euchirotidse," American Naturalist, May 1894, pp. 436-7 (figures in text). 2 Meckel (3) p. 260; and Duvernoy (4) p. 28. 3 P. Flourens, 'Mem. d'Anat. et de Phys. comp.-1. Etudes sur les lois de la symetrie dans le Regne Animal et sur la theorie du dedoublement organique,' Paris, 1884, pi. i. fig. 4. |