There are chapters in this little volume which will, I am afraid, be deemed too prolix by the general reader, and which yet the geologist would like less were there any portion of them away. They refer chiefly to organisms not hitherto figured nor described, and must owe their modicum of value to that very minuteness of detail which, by critics of the merely literary type, unacquainted with fossils, and not greatly interested in them, may be regarded as a formidable defect, suited to overlay the general subject of the work. Perhaps the best mode of compromising the matter may be to intimate, as if by beacon, at the outset, the more repulsive chapters; somewhat in the way that the servants of the Humane Society indicate to the skater who frequents in winter the lakes in the neighbourhood of Edinburgh, those parts of the ice on which he might be in danger of losing himself. I would recommend, then, readers not particularly palæontological, to pass but lightly over the whole of my fourth and fifth chapters, with the latter half of the third, marking, however, as they skim the pages, the conclusions at which I arrive regarding the bulk and organization of the extraordinary animal described, and the data on which these are founded. My book, like an Irish landscape dotted with green bogs, has its portions on which it may be perilous for the unpractised surveyor to make any considerable stand, but across which he may safely take his sights and lay down his angles.