I would also express my thanks to Professor Flower, Hunterian Professor at the Royal College of Surgeons, London, for his invariable courtesy in facilitating my examination of the ophiological specimens in the museum of that College, to which my honoured father (himself a member) attributed all the love of the study of natural history which from our earliest recollections were encouraged in his children. My thanks are also due to Dr. Günther of the British Museum for similar facilities there. Indeed, the words of encouragement given me, no less than six years ago, by the distinguished heads of the zoological department of our great national collection, sustained my courage in opposition to all counter influences _outside_ the British Museum. When first contemplating and presenting some outline of this work to Dr. Günther, he honoured me by expressing his opinion that such a book was ‘much needed;’ that it would be ‘extremely useful and interesting.’ He was even so kind as to promise to state this opinion in writing to any publisher who might consult him on the subject. I here claim the pleasure of thanking my present publishers for dispensing with the necessity of troubling Dr. Günther, and for entrusting me with the preparation of this book, which, before a chapter of it was completed, they engaged to publish. Deficient as I feel it to be, it is at length launched on the doubtful waters of public criticism. If any scientific eyes honour it with a glance, they will with clemency remember that, with no scientific knowledge whatever to start with, I have had to grope my way unaided, plodding over technicalities which in themselves were studies; and if, as no doubt is the case, any misapprehension of such technicalities has here and there crept in and misinterpreted the true meaning, I anxiously trust that the truth has not been altogether obliterated by such obscurities. In conclusion, let me not omit a grateful tribute to the invariable kindness of the heads of the Reading-Room at the British Museum; and for their assistance in obtaining books of which I might never have known. The kindness of Mr. Garnett extended even beyond the Reading-Room; for while I was invalided at the seaside, and could only read, _not write_, he translated and forwarded to me some important pages from Lenz, a German ophiologist. To him, therefore, the thanks of the reader are also due.