CROCODILIANS, LIZARDS, AND SNAKES. 695 



larger spaces toward the distal regions. In many species, especially 

 the Soleuoglypha, the distal part of the lung has very thin membranous 

 walls. In Chersydrus the reticulate structure continues to the extremity, 

 and the tracheal lung has no lumen. The left lung does not usually 

 extend beyond the gall bladder, but in Cliersydruf< it extends to the 

 anus. The post-tracheal or true lungs begin opposite the ventricle 

 of the heart, or just posterior to it. The rudimental right lung, when 

 present, is situated uear the apex of the heart. 



The condition of knowledge as to the character of the lungs of snakes 

 was stated by Stannius, in 1856,* as follows : 



The detailed accounts as to the single or double character of the lungs leave much 

 to be desired. Among Ophidia Angiostomata there possess a single sac, ii/u«o^>/i/« 

 and all TyphlopidcB which have been examined; as to the Tortricid;c [Ilysiidaj], 

 there are apparently species with two lungs {T.xenopeltis) l^Xenopeltis unicolorif 

 and others with a single lung (T. sci/tale) [_= Ilysia scytale]. Among Eurystomata, 

 all the Peropoda ( Z/oa, Python, Eri/s) possess apparently two lungs. The Calamarina 

 that have been investigated have one lung. Among Colubrina and Glyphodonta 

 there are great variations. All the Coronellce of Schlegel possess, according to 

 Schlegel, a single lung. I find the lung single in Rhachiodon scaber [^Dasijpeltia]. 

 Tropidonotus natrix [^Natrix vulgaris'] has a very small rndinieut of a second lung. 

 Coluber [Spilotesl variabilis possesses, according to Schlegel, the rudiment of a second 

 lung. According to the statement of Meckel, this rudiment is common in Coluber. 

 The Xenodous have, according to Schlegel, a single lung (X. severus and X.rhabdo- 

 cephalus). In Heterodon I find a rudimental second lung. The Lycodons, according 

 to Schlegel, iiossess a single lung; as also do PsammopJns and Hnmalopais. In Den- 

 drophis coluhrina Schlegel found the rudiment of the second lung. In Dipsas, accord- 

 ing to Schlegel, there are variations ; but he states that D. multimaciilafa, D. Iwris, and 

 D. annulata ISibon annulatum] have but otig lung. The Achrochordina have but one 

 lung. Among Hydrophidis I found in three species of Rydrophis the lung sac 

 simple. Meckel states that Platurus has a very small rudiment of a second lung. 

 Among the remaining poisonous snakes there is an insignificant rudiment of the sec- 

 ond lung in the Elapina and Crotalina ; while the Viperina possess an entirely simple 

 lung. 



In 1894 1 presented to the American Philosophical Society^ the results 

 of my studies on this subject, in which I added many observations to 

 those previously made, and discovered a number of important system 

 atic indications. I also found occasion to correct some of the state- 

 ments quoted by Stannius from Schlegel, as above noted. I give here 

 tlie results presented in that paper : 



The snakes with rudimental posterior limbs (Peropoda) show in the character of 

 their lungs what they show in the rudimental limbs themselves, and in the hemi- 

 penis, the nearest relationships to the Lacertilia. They possess, with an exception 

 to be noted later, two well- developed lungs, one of which is larger than the other. 

 The smaller lung lies to the right side and ventrally, while the larger one lies to the 

 left side and dorsally. In some species the dorsal and ventral relation is more pro- 

 nounced than in others. In the Colubroidea the right or ventral lung is generally 

 present, but of very much reduced proportions, the usual size being from 2-5 ram. in 

 length. It is connected with the other lung by a foramen, which perforates the 

 tracheal cartilage at a point a little beyond the apex of the heart, and opposite to 



' Zootomie der Amphibien, p. 108. 



^Proceedings Amer. Phil. Soc, XXXIII, 1894, p. 217. 



