interior of which country I penetrated to the distance of nearly four hundred miles from the coast-line, I despatched my able assistant, Mr. Gilbert, to explore the western and northern portions of the country, and returned to England in August 1840; I immediately commenced the work _de novo_, and the result of my labours is now before the public. It fortunately happened at the commencement and during the progress of the work, Her Majesty’s ships the Beagle, under the command of Captains Wickham and Stokes; the Britomart, under Captain Stanley; the Fly, under Captain Blackwood, and the Pelorus under Captain Chambers were employed in surveying the northern and north-western coasts of Australia; and the Erebus and Terror under Captain Sir James C. Ross, in a voyage of discovery towards the south pole. While engaged in the performance of their arduous duties, the officers of those vessels succeeded in procuring many interesting novelties, which, with the greatest liberality, were communicated to me for the present work, whereby its value has been much enhanced. This liberality will be found duly acknowledged in the histories of the species, for the use of which I am indebted to the kindness of B. Bynoe, Esq., Surgeon R.N., Lieut. Emery, R.N., Commander J. M. R. Ince, R.N., Edward Dring, Esq., Purser R.N., Dr. Robertson and Robert M’Cormick, Esq., Surgeons R.N., and John M’Gillivray, Esq. After spending two years in Western and Northern Australia, Mr. Gilbert returned to England in September 1841, bringing with him the result of his labours, which proved of sufficient value and importance to induce me to believe that much yet remained to be discovered in those countries, and to direct him to return thither, which he accordingly did in the ensuing spring; and after again visiting Swan River, and sedulously exploring the interior so far as practicable, he proceeded to Sydney, and, unfortunately for himself, allowed his love of science, in the advancement of which no one was more ardent, to induce him to join Dr. Leichardt in his overland journey from Moreton Bay to Port Essington. On this expedition, he, as usual, displayed his wonted zeal and activity until the 28th of June, when, the party being treacherously attacked by the natives, his valuable life was sacrificed, I lost a most able coadjutor, and science has to deplore one of her most devoted servants; fortunately, however, in despite of the many difficulties and dangers which beset the party during the remainder of their journey, his journals and notes, together with the specimens he had been able to procure, were preserved and transmitted to me by Dr. Leichardt, and proved of valuable assistance in determining the range of many of the species.