242 TEE POPULAR SCIENCE MONTHLY 



Near Buck creek itself the ant-hills contained only small sharks' 

 teeth, showing that they were still built over marine beds. Then as 

 one mounted the divide and with it crossed higher and higher strata 

 there was a long interval of totally unproductive formicaries, until the 

 principal bed of lignite was reached, and above this, at a vertical dis- 

 tance of ten to fifteen feet, the best of the ant-hills were found, which 

 contained among other remains the bones, scales and teeth of fresh- 

 water fishes allied to the gar-pikes living to-day in southern rivers. 

 These were carefully preserved for comparison with the mammal-bearing 

 sands at Yale collected by the older expeditions, and which were found 

 later to include, in addition to the mammals, fossils exactly similar to 

 those which we secured at this time. That we had found an old locality 

 was further proved by indications of a former camp, fire wood, rusted 

 tin cans, and in an adjacent ant-hill tiny, worn fragments of an unfor- 

 tunate investigator's spectacles ! 



The mammalian relics which were thus found were of very small 

 size, consisting of individual teeth or a fragment of a jaw with one or 

 more teeth still in position, or other portions of the bones. Mammal 

 teeth are fortunately highly indicative of habit and relationships; but 

 on the other hand, in collections of this sort, not one bone can be asso- 

 ciated with another. Thus, while some idea of the general size and 

 method of feeding may be obtained, no attempt to restore the skeleton 

 or even the entire skull is possible. In size none of the ant-hill mam- 

 mals was larger than a rat, and many were much smaller. Those whose 

 teeth bore few sharp-pointed cusps were carnivorous, feeding on such 

 feeble folk — insects, worms, and possibly other mammals — as they could 

 overcome. Others with chisel-shaped incisors and many-cusped grind- 

 ing teeth were plant-feeders, probably living not only on tender leaves, 

 but on berries and the seeds of berries and other fruits. 



The little glimpse of a former geologic age which this trip gave us 

 was full of suggestive detail. I have already described the scene as the 

 scientific imagination conjures it up, the broad, savanna-like, low-lying 

 lands over which wandered the huge reptiles then at the very culmina- 

 tion of their evolution. But what of the mammals ? Where were they 

 and how did they survive the competition with the dinosaurs ? Possibly 

 their very insignificance was their chief safeguard, just as countless 

 small rodents and insect-eating creatures live to-day in the lion- and 

 buffalo-haunted African jungles. Possibly they were tree-inhabitants, 

 and the location of the mammal-bearing ant-hills near the lignite cer- 

 tainly suggests an abundance of near-by vegetation. However we may 

 interpret it, the evidence is clear that these mammals and the dinosaurs 

 were contemporaries in the same general locality though the exact en- 

 vironmental conditions under which they lived may have differed. 



Passing back in time some millions of years further, one finds in 



