The sexes of this bird differ in size very considerably; and there are, also, variations in size and measurements, such as comparative lengths of their bills and tails between different specimens. We have seen a large number of specimens, from various localities, but of one species only. Though we have been constantly on the watch for it, we have never detected the smaller species alluded to by Captain McCown, which is very probably _Geococcyx affinis_, described by Dr. George Hartlaub, of the State Museum of Bremen, one of the most learned and accurate of European ornithologists. That species may be more an inhabitant of the mountainous or hilly country than the subject of our present article. [Illustration: Plate 37 The Whip-Tom-Kelly Vireosylvia altiloqua (_Vieillot_)] VIREOSYLVIA ALTILOQUA.—(Vieillot.) The Long-billed Flycatcher. The Whip-tom-kelly. The John-to-whit. PLATE XXXVII. Adult Male. This little bird is very similar in form and general appearance to the Red-eyed Flycatcher (_Vireosylvia olivacea_), of the United States, but is larger, and is distinctly characterized by the dark line on the side of the neck. It appears to possess much the same habits as the common species just mentioned, and others that inhabit the northern division of the continent of America. Passing its life, for the greater part, searching for insects amongst the thick foliage of the forest, in which its color favors concealment, it utters its peculiar notes, evidently of the same general character, but much louder and quite different from those of either of its northern brethren. Though long known as a bird of the West Indies, and represented by Mr. Gosse to be abundant in the Island of Jamaica, it has but recently been discovered within the limits of the United States. Vieillot, it is true, gave it as a North American species, and in his fine work, which is of standard value in the history of our birds, figures it accurately, but from specimens obtained in the West Indies. It was first ascertained to be a summer visitor in Florida, by Dr. A. L. Heermann, who observed it in considerable numbers in that State, at a season when it was certainly engaged in the duties of incubation; but it has as yet never been noticed in any other part of the United States. It is probable, too, that it inhabits Cuba, but the several able naturalists of that Island have not detected it, or at least have not stated it to be different from the common Red-eyed Flycatcher. For our article on this bird, Dr. Heermann has, with great kindness, furnished the following notice:—