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 discovered 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 New 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 surface, but in excavating their subterranean galleries the sand and other
Fig. 4. A Fossil bearing Ant-hill in which the Bones and Teeth of the tiny Warm-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, part way up the slope, while on the western and northwestern 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-
