The Dedication of a work like this, destined to preserve all the names it enrols in the sculpture-like immortality of science, naturally delays us for a moment. Of the foreign teacher and friend to whom the author owes some of his earliest lessons, and of that group of our own citizens, most of them still living, who lent their united efforts to the enterprise of publication after it was commenced, we need not speak individually. But we cannot pass over the name of FRANCIS CALLEY GRAY without a word of grateful remembrance for one who was the friend and adviser of the author in planning the publication of the work before us. We who remember his varied culture, his large and fluent discourse, with its formidable accuracy of knowledge and gracious suavity of utterance, his taste in literature and art, which made his home a suite of princely cabinets, his generous and elegant hospitality, which scholars and artists knew so well,--counting him as the peer, and in many points the more than peer of such as the wide world of letters is proud to claim,--are pleased to see that his cherished name will be read by the students of unborn generations on the first leaf of this noble record of the science of our own. The PREFACE which follows the Dedication is full of grateful acknowledgments to the many friends of science, in all parts of the country, who came forward to lend their aid in various forms, especially in collecting and transmitting specimens from the most widely remote sections of the continent. The pious zeal of Mr. Winthrop Sargent, who brought a cargo of living turtles more than a thousand miles to the head-quarters of testudinous learning at Cambridge, is only paralleled by the memorable act of the Pisans in transporting ship-loads of holy soil from Palestine to fill their Campo Santo. Genius is marked by nothing more distinctly than that it makes the world its tributary. He from whose lips it speaks has but to look calmly into the eyes of dull routine, of jaded toil, of fickle childhood, and utter the words, "Follow me." Custom-house officials close their books, tired fishermen leave their nets, riotous boys forsake their play, to do the master's bidding. Is he making collections for some great purpose of study? Piece by piece the fragmentary spoils flow in upon him, of all sizes, shapes, and hues; a chaos of confused riches, perhaps only a wealth of rubbish, as they lie at his feet. One by one they fall into harmonious relations, until the meaningless heap has become a vast mosaic, where nothing is too minute to fill some interstice, nothing too angular to fit some corner, nothing so dull or brilliant of tint that it will not furnish its fraction of light or shadow. Such has been the history of those years of labor the results of which these volumes present to us. Whatever may have been said of the devotion of our countrymen to material interests, the wise and winning lips