Since its foundation as a Science, at the beginning of this century, by the illustrious Cuvier, Palæontology has progressed with an astonishing rapidity; and though theoretically belonging to the twin sciences of Zoology and Botany, its domain is now so vast, and the number of facts which it has accumulated is so great, that it has every claim to rank as a distinct department of knowledge, which cannot be fully mastered except by those who make it the subject of special study. That the number of these is daily increasing is shown conclusively by the increased number of systematic works on Palæontology which have appeared of late years, and not less by the character of these. Two of these treatises, both as yet but partially published, may be singled out for mention in this connexion—namely, the “Handbuch der Palæontologie” by Professors Zittel and Schimper, and the new “Lethæa Geognostica” by an association of German palæontologists. The former of these, if carried out with the fulness and accuracy which distinguish its first portion, will be one of the most valuable and important treatises on systematic palæontology which we possess in any language, and will be a fitting companion to the classical treatises of Pictet and D'Orbigny, though it will not supersede either of these honoured works. Of the second of these only the first part, embracing the Atlas of Plates of Palæozoic fossils, has as yet been issued; but if the text be equal to the plates, and if the various sections of the work are undertaken by men as eminent as Ferdinand Roemer, the new “Lethæa Geognostica” will undoubtedly form an indispensable item in the library of every working palæontologist.