INNOCUOUS SERPENTS. 
137 
The second genus of Terrestrial Serpents is the 
XENODON. 
These may be considered as Coronellae, mostly of a 
large size, with a lumpish form, a large head, a short or 
truncated muzzle, a thick trunk, and flattened belly. We 
perceive in their upper jaw a solid posterior tooth, very 
long and compressed. Their scales are smooth, and dis- 
posed in very oblique rows, especially on the neck, which 
is very expansible ; and has the ribs less curved than or- 
dinary, in which the animals approach the Najas. The 
plates on the head are squat and broad. This genus is 
not rich in species, and the Xenodon belongs to the class 
of rare serpents which inhabit, in small numbers, the hot 
and temperate climates of both worlds ; not a single spe- 
cies is known in Africa, nor in New Holland. Some pre- 
fer a humid situation ; but others, that delight in dry 
places, depart from the typical species to approach the fol- 
lowing genus, the Heterodon. 
1. Xenodon Severus of Surinam and Brazil unites 
especially the characters which we have assigned to these 
animals in general. It has all its parts very heavy and 
thick, and the plates on its head short and broad. The 
lung, enveloping the trachea, occupies the space between 
the heart and the throat. The ground is of a pale brown- 
ish-yellow, ornamented above by a dozen of dark ocel- 
lated spots, extremely broad. We perceive on the head 
several transverse bands, and angular marks on the oc- 
ciput. The colours in adults are so effaced, that their 
original disposition can with difficulty be traced. I have 
seen individuals of an uniform red, while others were of a 
brown-green ; S. 140 -f 36. B. S. 21. It is a serpent of 
large size, which appears to feed exclusively on the great 
frog of South America, and which swims with much dex- 
terity. 
2. Xenodon Bhabdocephalus of Brazil is so near the 
preceding, that they seem only to form one species, dis- 
tinguishable by a form a little more elongated, from which 
results a number of scuta, varying from S. 140 + 44 
M 
