One of our most able biologists, A. R. Wallace, in his _Geographical Distribution of Animals_,[106] informs us that ‘the _Crotalidæ_, including the deadly rattlesnakes, abound most in the oriental regions’ (though not a single rattlesnake is found there, or in the Old World at all). Let us seek for the reason of this apparent incongruity, and how it is that a large number of serpents which have no rattle come to be placed among those which have an instrument specially constructed to produce a rattling sound. Not to weary the reader by attempting to describe the various systems of classification adopted by the many herpetologists who were the contemporaries and immediate successors of Linnæus, we will rather invite his imagination to picture the geographical history of our globe during that age. Travels, explorations, the establishment of new colonies, and the settlement of new territories marked the era; and, as a sequence, new and hitherto unknown fauna were continually brought home to Europe. We have seen, too, how natural history had been growing into a science, and how travellers and zoologists stimulated each other by their researches and writings. To recall a few of the names with whom reptiles are associated, and to remind the reader that one arranged them according to their scales, another their form, a fourth their teeth, a fifth their habits, and so on, and that even at the present day the classification of them is far from complete, the present writer will be absolved from attempting anything beyond generalization. Studying snakes towards the end of the last century, were Laurenti, Buffon, Bonnat, Lacepède, Klein, Seba, etc.