REPTILIA 255 



and throat is astonishing. A full grown Chameleon will catch, 

 chew, and swallow the largest moth." 

 While we may object to the statement that a Chameleon "pauses 

 to think" or "knows perfectly well," we cannot but admire the vivid- 

 ness of the verbal picture here presented. 



Division II. Ophidia (Snakes) 



Snakes may be defined as Sauria or Squamata that have the right 

 and left halves of the lower jaw connected with an elastic ligament, 

 which enables the mouth to stretch much more widely than it other- 

 wise could; they are limbless or at best have rudimentary limbs under 

 the skin, as in the pythons. They represent a more advanced stage of 

 specialization than do the lizards and are a much more modern devel- 

 ment than any of the other living reptilian groups. In certain respects 

 the snakes are degenerate. As in the eel-like fishes and amphibians 

 the greatly elongated body is accompanied by loss of limbs. 



The majority of the snakes have the quadrate very loosely articu- 

 lated with the squamosal; which aids in increasing the gape of the jaws 

 and enables snakes to swallow objects greater in diameter than their 

 own bodies. This is well shown in the illustration (Fig. 141, A) repre- 

 senting a python swallowing a large bird. 



The vertebral column consists sometimes of nearly three hundred 

 vertebrae, which are little if at all specialized in the different regions 

 of the body. The skin is covered with scales devoid of bony cores. 

 The ventral scales are usually broad, band-like and erectile, and are 

 used as an accessory to locomotion; for they point backwards and 

 thus give a good friction surface against the ground or trunks of trees. 

 The outer skin is shed several times a year all in one piece. The eyes 

 have no lids, but each eye is covered with a watch-glass-shaped mem- 

 brane which is transparent and is shed when the rest of the skin is 

 moulted. This explains why the snake is blind shortly before and 

 during the moult; for the dead eye-membrane is opaque. The ear is 

 peculiar in that the columella has a fibrous pad at the outer end, which 

 plays against the quadrate; so that when the quadrate is pulled away 

 from the skull in swallowing, the columella must be so dislocated as 

 to produce a tremendous roaring sensation, if the auditory organ is 

 at all sensitive. Fortunately, perhaps, the snake has not a keen sense 

 of hearing. The tongue is very slender and forked and is used as a 



