190 REPTILIA. 



dilatation, the occiput is more or less enlarged, and the tongue 

 forked and very extensible. 



They have long been divided into two principal genera, Boa and 

 Coluber, distinguished by the simple or double plates on the under 

 part of the tail. The genus 



Boa, Lin.(l) 

 Formerly comprized all those Serpents, venomous or not, the under part 

 of whose body and tail is furnished with uninterrupted, transverse scaly 

 bands, and which have neither spur nor rattle at the end of the tail. As 

 they are rather numerous, even after deducting the venomous species, the 

 others have been again subdivided. 



The Boa, properly so called, has a compressed body, thickest in the 

 middle, a prehensile tail, and small scales on the head, at least on its poste- 

 rior portion. It is in this genus that are found the largest Serpents on the 

 globe; certain species attain a length of thirty or forty feet, preying on 

 Dogs, Deer, and even Oxen, which they manage to swallow entire, after 

 having ci-ushed them in their folds and covered them with saliva. This 

 operation requires much time and an enormous dUatation of their jaws and 

 throat. Their smaU lung is but half the length of the other. 



Boa constrictor, L. Known by a broad chain, which extends along the 

 back, formed alternately by large, blackish, irregularly hexagonal spots, 

 and by pale oval ones, the two ends of which are emarginate. 



The celebrated Anaconda is a true Boa. 



Coluber, Lin. 



This genus comprised all those Serpents, venomous or not, whose sub-cau- 

 dal plates are divided in two, that is, which are arranged by pairs. 



Independently of the subtraction of the venomous species, their number 

 is so enormously great, that naturalists have had recourse to all sorts of 

 characters to subdivide them. 



In the subgenus PytJum we find the Col, javanicus, Sh., which has been 

 found thirty feet in length. Sunda Islands. 



Serpents which are venomous par excellence, or those with iso- 

 lated fangs, have their organs of manducation constructed on a very 

 peculiar plan. 



Their superior maxillary bones are very small, attached to a long 



(1) Boa, the name of certain Italian Serpents of great size, most pro- 

 bably the four striped Coluber, or •' Serpent of Epidaurus" of the Latins. 

 Pliny says they were thus named, because they sucked the teats of Cows. 

 The Boa, 120 feet long, which it is pretended was killed in Africa by the 

 army of Regulus, was probably a Python. See Pliny, lib. VIII, cap. xiv. 



