838 The American Naturalist. [Oetolier, 
I have referred to the dorsal and ventral positions of the two 
lungs. The rudimental lung is to the right of the dorsal lung 
in the Colubroidea, but in the Ilysiide it is to the left. It is quite 
questionable which lung this rudiment in this family really 
represents. In the Typhlopide, the single lung is on the right 
side and extends from the heart to the liver. It has the posi- 
tion of the rudiment lung of the Colubroidea, and may repre- 
sent it. I cannot decide this question without further material. 
In Glauconia there is but one true lung, and this is ventral in 
position, and originates to the right of the heart, so that in 
this genus also it may represent the rudimental lung of the 
Colubroidea. There is here no tracheal lung or organ. 
I have no doubt of the propriety of the separation of the 
Ungualiide from the other Peropoda, on account of its pul- 
monary characters. Nor is there any doubt in my mind of 
the necessity of the separation of the Leptognathinz from the 
Xenodontinz, on account of its large tracheal lung. The genus 
Heterodon differs very much from other Xenodontinz, in the 
possession of an enormous diverticulum of the lung, but as it is 
not present in the allied genus Lystrophis Cope, its wider dis- 
tinction may be a questionable proceeding. The very marked 
characters of the genus Chersydrus characterize the family, as 
well as the osteological characters. It remains to be seen 
whether the family I termed the Nothopidex, but which Bou- 
lenger unites with the Chersydridi, agrees with it in pulmo- 
nary characters. The remarkable tracheal lung or gland dis- 
tinguishes the .Epanodonta from the Catodonta, emphasiz- 
ing the differences observed in the osteology of the skull. 
The value of the rudimental right lung as a character of the 
Colubroidea is increased by my investigations. In only two 
genera have I found it present or absent, viz, Halsophis and 
Pityophis. Iam not sure but that I may yet find it in the 
P. melanoleucus, 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 Colubrins, appears fo 
be characterized by its absence, viz., Rhinochilus, Cemophora 
and Ophibolus; all genera with an entire anal shield. The 
development of cartilages in the bronchial foramen or tube of 
