702 REPORT OF NATIONAL MUSEUM, 1898. 



Ill Solenoglypha tlie geuus Atractaspis is spinous to the apex, appar- 

 ently on a longitudinally laminate basis. In the Viperidae and Crotal- 

 idie the spines are on a flounced basis. The apices are calyculate in 

 Bitis, Clotho, and Vipera, and spinous in Cerastes. They are calycu- 

 late in Crotalidae, in Bothrops, Ancistrodon, Sistritrus, Crotalus, and 

 JJropsophus. In Crotalus {durissus of the Neotropical fauna) the median 

 spines are replaced by papillae; in all the other genera they are spinous. 



II. SYSTEMATIC CONSIDERATIONS. 



Diversity of lung structure accompanies the primary groups which 

 are characterized by peculiarities of the skeleton to such a degree tbat 

 we are warranted in according it a high systematic value. Thus 

 Angiostomatous and Peropodous snakes have two lungs, while the 

 Colubroidea have one and a rudiment, and the Solenoglj^pha always 

 have a tracheal lung. Exceptions and variations from these rules thus 

 become of importance. Thus I have no doubt of the propriety of the 

 separation of the Ungaliidse from the other Peropoda, on account of 

 its pulmonary characters. Nor is there any doubt in my mind of the 

 necessity of the separation of the Leptognathiuft from the Xenodon- 

 tinae, on account of its large tracheal lung. The very marked charac- 

 ters of the genus Chersydrus characterize the family, as well as the 

 osteological characters. It remains to be seen whether the family I 

 termed the Nothopidae, but which Boulenger unites with the Chersy- 

 dridiie agrees with it in pulmonary characters. The remarkable 

 tracheal lung or gland distinguishes the Epanodonta from the Cato 

 donta, emphasizing the differences observed in the osteology of the 

 skull. The huge diverticulum of Heierodon serves to distinguish the 

 genus from its allies. The extraordinary transverse dilatation of the 

 trachea in Thrasops establishes the genus as distinct. 



The value of the rudimental right lung as a character of the Colu- 

 broidea is increased by my investigations. In only two genera have 

 I found it either present or absent, namely, Halsophis and Pityophis. I 

 am not sure but that I may yet find it in the P. nielanoleucus, where I 

 have failed hitherto, but I am sure that it is present in some species 

 of Halsophis and wanting in others. A natural group of American 

 Colubrinae, appears to be characterized by its absence, namely, Rhino- 

 chilus, Gemophora, and Ophiholus; all genera with an entire anal shield. 

 The development of cartilages in the bronchial foramen or tube of 

 the rudimental lung is not a constant character. I found it in one 

 Heterodon platyrhinus and not in another; it is present in Conophis 

 pulcher, but absent in C. sumichrastii. 



The numerous characters presented by the hemipenis have various 

 values. Several very distinct types are distinguishable, but they are 

 continuous at some point, through intermediate forms. This is, how- 

 ever, the history of all characters which distinguish organic beings, 

 especially of those which have been relied on as characters of the 



