INNOCUOUS SERPENTS. 137 



The second genus of Terrestrial Serpents is tlie 



XENODON. 



These may be considered as Coronellae, mostly of a 

 large size, with a lumijish 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 dehght 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 gi^ound is of a pale brown- 

 ish-yellow, ornamented above by a dozen of dark ocei- 

 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-gi-een ; S. 140 -f- 36. R. 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 Rhabdocephalus 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 -j- 44 



