702 MB. GERARD W. BUTLER OX THE [NoV. 19, 



urgans (oesophagus, and aortic roots, &c.), explain the deceptive 

 position of the rudimentary left lung. 



Only one or t^\•o Snakes among those which I have examined 

 are so" deceptive as Heterodon platyrliinus, in the matter of the 

 situation of the 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 my 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 dis- 

 placements 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, correspouding 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 Hver towards 

 the right side. 



'o'- 



IV. On the Cosiplete or Partial Suppression of the 

 Right Lung in AmphisbjENId^. 



A reference to the list on p. TOG (which includes species of all 

 the genera of AmphislianidcB in the British Museum Catalogue, 

 with the exception of the rare forms Vhirotes, Rhineura, and 

 Agamedon) shows that with the exception of Trogonophis iviegmanni, 

 and to a lesser extent of Pachy calamus brevis, the right lung is 

 rudimentary or absent altogether in all the Amphisbseuidse ex- 

 amined, while in these two it is distinctly smaller than the left. So 

 far, then, as my observations go, this would seem to be a character- 

 istic peculiarity of the Amphisbajnidfe. 



As to Chiro'tes'^ two writers ^ have made themselves responsible 

 for the statement that the right lung is much larger than the left ; 

 w-hile a third ^ 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 vie\^- is correct. As Chirotes 

 differs markedly from the other Amphisba^nidaj 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, CJnrotes is an Amphisbaenid, there is a certain pre- 



^ For a preliminarv notice of a division of these animals into three genera, 

 see Cope, " On 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. 



^ r. 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. 



