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THE POPULAR SCIENCE MONTHLY 



dinosaur material from this region was collected by John B. Hatcher, 

 a graduate of Yale, and so thoroughly was his work done that very 

 little sign of them now remains. What we of the present expedition 

 especially desired, however, was not to find more dinosaurs, but to hunt 

 for the remains of the tiny mammals, the forebears of the warm-blooded, 

 furry quadrupeds of to-day, which carried on a precarious existence in 

 the midst of such stalking terrors as the giant reptiles. 



These mammal remains are known from but few Mesozoic localities 

 and are valued proportionately. By some lucky chance it was dis- 

 covered that, although they might be found imbedded in the sediments, 

 the most productive places, curiously enough, were the ant-hills. These 

 are numerous and huge though in no way differing from those I have 

 found in Xew England except in the contained fossils. The ants are 

 a lusty breed, valiantly uniformed in brown and black, and with very 

 effective stings, as we have good reason to know. In building their 

 formicaries they not only collect material from the surrounding sur- 

 face, but in excavating their subterranean galleries the sand and other 



Fig. 4. A Fossil-beaking Ant-hill in which the Bones and Teeth of the tiny 



Wakm-blooded Mammals are found. 



particles are deposited on top of the growing pile. This was generally 

 a very symmetrical cone with the entrance almost invariably on the 

 eastern side, pait way up the slope, while on the western and north- 

 western aspects the grains of sand were somewhat coarser. We found, 

 however, on breaking into the nest, that the immediate surface was 

 somewhat hardened so as to be distinctly crust-like, while within, until 

 one came to the well-built tunnels, coarse and fine sands were inter- 



