136 BRITISH LIZAEDS 



type and the absolutely limbless species of which the 

 slow-worm is an example. 



It has been said that a burrowing habit, or a life 

 amidst sand, might be regarded as conditions under 

 which limbs would be not altogether an advantage, 

 and, as a matter of fact, it will be found that it 

 is precisely in those lizards which live under these 

 conditions nowadays that this partial or complete 

 absence of limbs is to be observed. It is, too, almost 

 certain that the laws of the past in biology have been 

 very similar in their methods of operation to those of 

 the present. 



Along with this reduction in the size of the limbs 

 in lizards is found an elongated trunk or body, 

 approaching the shape of that of a serpent. This is 

 seen, for example, in the slow-worm. This long body 

 may be associated with a shortened tail or not ; in 

 the slow-worm the tail is as long as the body. In 

 many-limbed lizards the tail is, of course, considerably 

 longer than the body, as in the viviparous lizard. 

 Then we find that in the limbless lizards there are 

 some vestiges of the limbs or limb girdles usually 

 found under the skin. Those of the hind-limbs lie 

 immediately in front of the anal aperture. A very 

 interesting point is that the fore-limbs disappear 

 before the hind-limbs, or are frequently smaller than 

 the hind-limbs. Some species have hind-limbs only, 

 while rarely the opposite condition occurs, e.g. in 

 Chirotes canaliculatits, a species found in Mexico and 



