THE RATTLESNAKE 149 



whole order of serpents. It is also a member of an ordei 

 of reptiles not yet certainly known to have extended 

 back beyond tertiary times, but which is now disseminated 

 throughout all the warmer regions of the habitable globe. 

 It must have had four-footed ancestors, though it has 

 not the smallest relic of a limb to boast of itself. As to 

 what those four-footed creatures were like we cannot as 

 yet hazard a conjecture. Since perfectly developed 

 serpents, and even vipers, existed in tertiary times, it 

 seems unlikely that any lizards of our own day can 

 represent what were once the predecessors of all ser- 

 pents. It is possible that in the before-mentioned 

 python-headed reptiles of America, we have cousins 

 of the ancestors of snakes, if not the ancestors them- 

 selves. But this is still but a speculative hypothesis in 

 which we cannot venture to repose anything like 

 confidence, impressed as we are with the constantly 

 recurring evidence before us that many similarities of 

 organisation may co-exist without any true affinity of 

 race and descent, accompanying such co-existence. 

 The ancestors of the rattlesnake are, therefore, beyond 

 our mental vision. All but enthusiastic naturalists 

 will probably desire that their progeny may, within a 

 moderate period, be beyond our bodily vision also. 



