Obs. We are acquainted with no species of Gull which intimately resembles the bird now described. Judging from the only description extant of _Larus Belcheri_. Vigors, which is in the Zoological Journal, Vol. IV. p. 358, and which is too short to be of service in this family of birds—it appears to resemble that species to some extent. _L. Belcheri_ is much larger, and is described as having the entire plumage brownish lead-color, and as being 21 inches in total length. It appears to be, however, the only western American species with which our present bird can be confounded. [Illustration: Plate 6 The Northern Sea Eagle Haliaëtus pelagicus (_Pallas_)] HALIAETUS PELAGICUS.—(Pallas.) The Northern Sea Eagle. PLATE VI—Female. The study of the rapacious birds of western and north western America presents great attractions to the ornithologist, and a wide field for discovery. Owing, principally, to the difficulties in obtaining, or even in observing the shy and vigilant birds of this family, their investigation is of peculiar character, and dependent on accidental opportunity in some measure every where, but especially in countries where the primitive forests yet flourish in undisturbed vigour, and which abound in unexplored and, as yet, inaccessible mountains; or in plains of an extent only known to the adventurous hunter, and traversed only by the wandering Indian, or by the pioneers of civilization: the devoted missionary, or the enterprising and hardy emigrant. Such is the character of the regions of that portion of North America, the visits of naturalists to which have been too transient to afford proper opportunities for the study of the rapacious birds, and the detached items of information which have appeared from time to time are not sufficiently numerous to be regarded as giving any clear insight into their history. The naturalist, generally travelling expeditiously with a military or other party on business for the government, or with a caravan of emigrants, may get a glimpse of a Falcon of singularly novel and beautiful plumage as it darts away into concealment; or may see, occasionally, an Eagle seated at ease, and viewing the novel cavalcade leisurely, but beyond the range of his rifle; or as he performs, in turn, his assigned duty, and guards his sleeping companions in the encampment, his watch-fire may attract clamorous night birds of strange forms whose cries are unfamiliar to him, but to his practised ear may present unmistakable family relationship, yet it is readily demonstrable that the proper study of those birds requires facilities of a description only attainable in the course of more protracted residence and frequently recurring opportunities.