THE CLASSIFICATION" OF THE OPHIDIA. 187 



vertebral hypapophyses continued to the tail, as in the truly venomous forms. Bou- 

 lenger has since found this character in a good many forms which I had not examined 

 and -which have no affinity to the water snakes. This character, while important, 

 presents the same evanescent stages in certain types that the dental characters before 

 noticed exhibit. It had long appeared to me that the only prehensile organs possessed 

 by serpents, the hemipenes, might probably present structural variations expressive of 

 affinity or diversity. In 1893 * I examined these structures in many of the leading- 

 types and was gratified by the discovery of a great many structural characters. In 

 fact these organs exhibit a variety of ornamentation and armature beyond any part of 

 the anatomy in the Ophidia, and I am satisfied that they furnish more important indi- 

 cation of near affinity than any other part of these reptiles yet examined. 'No one 

 hereafter can be sure of the place of a serpent in the system until the hemipenis has 

 been examined. 



Still another part of the structure remained to be studied. The assymmetry of 

 the lungs of snakes had often been noted by anatomists, but very little was known as 

 to the range of variation. Accordingly, when I undertook f a study of the pulmonary 

 organs, I was able to confirm observations previously made by Schlegel and Stannius, 

 and to correct some others, and to add a great number of facts as to species not pre- 

 viously examined. I give the details observed in the following pages. One result is 

 that I am able to confirm the conclusion of Boulenger, i. e., that the Colubriform 

 venomous snakes, the Proteroglypha (cobras, Elapes, etc.), do not differ in any funda- 

 mental respect from the non-venomous Colubridae, aud that they cannot be character- 

 ized as a suborder. The suborders then are: 



Catodonta (Type Glauconia). 



Epanodonta (Type Typhlops). 



Tortricina (Ilysiidse and Rhinophidse). 



Colubroidea (Peropoda, Asinea, Proteroglypha and Platycerca). 



Solenoglypha (Typical venomous forms). 



I. THE HEMIPENIS. 



The hemipenis is a projectile organ in the form of a hollow tube whose base is on 

 one side of the middle line and which opens into the anus. When retracted it lies 

 beneath the tail, extending for a greater or less distance, and terminating in a cylin- 

 drical muscle. This has considerable length and is finally inserted on a caudal verte- 

 bra. When the organ is projected this muscle is drawn forwards so as to evaginate the 



* American Naturalist, 1893, p. 477 ; 1894, p. 831. 

 \ Proa. Amer. Philos. Soc, 1894, p. 217. 



