BOIDAE 



597 



have been grouped into many genera, on unimportant characters, 

 referring to the scales and shields of the head. It is doubtful if 

 they are natural groups, a consideration which detracts much 

 from their value in the study of geographical distribution. 

 Even the two sub -families are not free from this reproach. 

 The range of the family is world-wide, Boidae occurring in all 

 tropical and sub -tropical countries, including islands, except 

 New Zealand. A few species live in South -Eastern Europe 



Fig. 156. — A, Ventral, B, dorsal, view of the skxiU oi Eunectes murinus. 

 Lettering as in Fig. 155. x 1. 



{Eryx) and in North-Western America. They mostly prefer 

 wooded districts, especially forests; climbing trees, assisted by 

 the short and partly prehensile tail. Others are semi-aquatic, 

 and a few live in sandy localities. They are all rapacious, and 

 by preference feed on warm-blooded creatures, which they con- 

 strict by coils of the body in order to hold, kill, and crush the 

 victim before swallowing it. Exaggerated notions are enter- 

 tained about their swallowing capacity. It is obvious that a 

 large snake, 20 feet long, half a foot thick, and weighing 

 several hundred pounds, can crush a tiger, a stag, or even a 



