THE RATTLESNAKE 145 



which may have been such predecessors. They were 

 gigantic, long-bodied animals, sometimes forty feet long, 

 with two pairs of limbs in the form of small paddles, and 

 were somewhat python-headed. They had jaws which 

 could be dilated to a certain extent like those of serpents. 

 But, as we have seen, it is not all snakes which possess this 

 power, and since these American giants must have gained 

 this power independently, it is difficult to see why the ser- 

 pents of later times may not have done likewise. True and 

 undoubted snakes, however, began to make their appear- 

 ance in the lower tertiary rocks. They were mostly large- 

 sized and seem all to have been non-venomous, though 

 a fossil viper has been discovered in the middle tertiary 

 rocks of the south of France. 



Arhong living reptiles we can hardly expect to find the 

 representatives of snake ancestors amid either tortoises 

 or crocodiles, but in the very extensive order of lizards 

 we might hope to find such, and indeed various kinds 

 of Hzards do seem to show some special resemblance 

 to snakes, although they are probably but superficial 

 ones. 



The most obvious distinction between snakes and 

 almost all lizards, is that the latter have two pairs of 

 limbs, while the former have not one. But among the 

 lizards known as seines (whereof one was a favourite 

 ingredient in the medicines of former days), the limbs, 

 as we go through a long series of forms, become smaller 

 and smaller, till they become as minute pi'oportionally as 

 are those of the batrachian amphiuma.* Some of these 

 lizards have a single pair of limbs, the hinder ones, while 

 the body is extremely elongated. Certain Australian 

 lizards {Delma) have no fore limbs, while the hind limbs 

 are only represented by a minute pair of flattened lobes, 

 * See ante, p. 109. 



it 



