482 The American Naturalist. 
Attenuate. Uromacer. 
Dipsadiform. Leptognathust, Mesopeltist. 
The genera of this subfamily in which the surface is exclusively 
gitudinally plicate are marked with a star; on the other genera 
more or less reticulate. The genera in which the extremity is spir 
are marked with a f. In Theleus the hemipenis is simple, and 
apex is covered with short separate papille, below which it is coar 
spinous; type Boodon virgatum Hallow. from W. Africa. Li 
is established on Herpetodryas bernieri of Madagascar, and rel 
species, on account of the absence of calyculi, and weak develo 
of spines of the hemipenis, and the isodont dentition. The 
Acanthophallus is designed to include the species formerly refe 
to Xenodon in which the hemipenis is spinous to the extremity. 
pe is X. colubrinus Gthr; the anal plate is entire. In Xen 
the extremity is smooth and plicate, and the anal plate is divided. 
SCYTALIN®. 
Fusiform. Wydrocalamus.t 
Colubriform. Pseudophis; Erythrolamprus*; Tachymenis+; Coniophanes; 
phis; Rhinostoma; Scytale; Oxyrrhopus; Tomodont; Thamnodynastes 
cludes Tachymenis hypoconia M.), Tropidodryas; Philodryas; Jaltris.* 
Altenuate. Langaha. 
As in the Xenodontine, genera with the apex plicate only at 
marked with a star, and those with a spinous apex are marked with 
dagger. The only species of Tomodon I have examined is the T. 
latus, which is not the type. The position of Langaha I am not 
fied about, as it may be an attenuate form of the Natricide. 
NATRICID#. 
This family, which I first defined from vertebral characters, is g 
ally easily distinguished from the others by the characters of its 
