It must not be overlooked that both Dr. Koch and the Illinois survey mention flint arrow and spear-heads as well as stone axes as being associated, directly or indirectly, with the remains of extinct animals. These stone axes undoubtedly were _ground_ implements; for, had they differed in any way from the ordinary Indian manufactures of the same class, the fact certainly would have been noticed by the observers. Thus far, then, we are not entitled to speak of a North American palaeolithic and neolithic period. In the new world, therefore, the human contemporary of the Mastodon and the Mammoth, it would seem, was more advanced in the manufacture of stone weapons than his savage brother of the European drift period, a circumstance which favors the view that the extinct large mammalia ceased to exist at a later epoch in America than in Europe. The remarks of Lieutenant-Colonel C. H. Smith on this point are of interest. "Over a considerable part of the eastern side of the great (American) mountain ridge," he says, "more particularly where ancient lakes have been converted into morasses, or have been filled by alluvials, organic remains of above thirty species of mammals, of the same orders and genera, in some cases of the same species, (as in Europe,) have been discovered, demonstrating their existence in a contemporary era with those of the old continent, and under similar circumstances. But their period of duration in the new world may have been prolonged to dates of a subsequent time, since the Pachyderms of the United States, as well as those of the Pampas of Brazil, are much more perfect; and, in many cases, possess characters ascribed to bones in a recent state. Alligators and crocodiles, moreover, continue to exist in latitudes where they endure a winter state of torpidity beneath ice, as an evidence that the great Saurians in that region have not yet entirely worked out their mission; whereas, on the old continent they had ceased to exist in high latitudes long before the extinction of the great Ungulata."[5] Flint implements of the European "drift type," however, are by no means scarce in North America, although they cannot (thus far) be referred to any particular period, but must be classed with the other chipped and ground implements in use among the North American aborigines during historical times. [Illustration: Fig. 2.]