190 THE CLASSIFICATION OF THE OPHIDIA. 



In examining the structure of the hemipenis the organ must he laid bare in situ 

 and split lengthwise along the exposed (inferior) middle line before it is removed. 

 This is necessary to avoid cutting it along the sulcus, which extends along the side. 



II. THE PULMONARY STRUCTURES. 



The condition of knowledge as to 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 leaves much to be desired. Among Ophidia Angiostomata there possess a single 

 sack, lihinophis and all Typhlopidae which have been examined ; as to the Tortricidse 

 [Ilysiida?] there are apparently species with two lungs (T. xenopeltis) [= Xenopeltis 

 unicolorj and others with a single lung (T. scytale) [= Ilysia scytale]. Among 

 Eurystomata, all the Peropoda (Boa, Python, Eryx) possess apparently two lungs, 

 The Calamarina that have been investigated have one lung. Among Colubrina and 

 Glyphodonta there are great variations. All the CoronellaB of Sehlegel possess, 

 according to Sehlegel, a single lung. I find the lung single in RhacModon scaber 

 [Dasypeltis]. Trojndonotus matrix [Natrix vulgaris] has a very small rudiment of a 

 second lung. Coluber [Spilotes] variabilis possesses, according to Sehlegel, the rudi- 

 ment of a second lung. According to the statement of Meckel, this rudiment is 

 common in Coluber. The Xenodons have, according to Sehlegel, a single lung (X. 

 severus and X. rliabdocplialus). In Heterodon I find a rudimental second lung. The 

 Lycodons, according to Sehlegel, possess a single lung, as also do Psammophis and 

 Homalopsis. In DendrojJiis colubrina Sehlegel found the rudiment of the second 

 lung. In Dipsas, according to Sehlegel, there are variations ; but he states that 

 D. muUimaculata, D. Icevis and D. annulata \_Sibon annulatum] have but one lung. 

 The Aehrochordina have but one lung. Among Hydrophidas I found in three species 

 of Hydrophis the lung-sack 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 second lung in the Elapina and Crotalina, while the 

 Viperina possess an entirely simple lung." * 



An examination of about one hundred and fifty species of nearly all types yielded 

 the following results : 



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 hemipenis, 

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

 noted later, two well-developed lungs, one of Avhich is larger than the other. The 



* Stannius, Zootomie der Amphibien, p. 108. 



