226 A BOOK-LOVER'S HOLIDAYS 



covered with water. In part of the area these 

 pits and pools of tar have existed for scores of 

 thousands or hundreds of thousands of years, 

 since far back in the Pleistocene. They then 

 acted as very dangerous and efficient mammal 

 traps and bird traps — and now continue so 

 to act, for the small mammals and the birds 

 of the neighborhood still wander into them, 

 get caught in the sticky substance, and die, as 

 I have myself seen. Moreover the tar serves 

 as a preservative of the bones of the creatures 

 that thus perish. In consequence some of the 

 ancient pits and pools are filled with immense 

 masses of the well-preserved bones of the strange 

 creatures that were smothered in them ages 

 ago. 



Nowhere else is there any such assemblage 

 of remains giving such a nearly complete pic- 

 ture of the fauna of a given region at a given 

 time. A striking peculiarity is that the skeletons 

 of the flesh-eaters far surpass in number the 

 skeletons of the plant-eaters. This is something 

 almost unique, for of course predatory animals 

 are of necessity much less numerous than the 

 animals on which they prey. The reversal in 

 this case of the usual proportions between the 

 skeletal remains of herbivorous and carnivorous 

 beasts and birds is due to the character of the 



