There is something very grotesque in the appearance of all the Puff birds; and their habits, in a state of nature, are no less singular. They frequent open cultivated spots near habitations, always perching on the withered branches of a low tree; where they will sit nearly motionless for hours, unless, indeed, they descry some luckless insect passing near them, at which they immediately dart, returning again to the identical twig they had just left, and which they will sometimes frequent for months. At such times the disproportionate size of the head is rendered more conspicuous by the bird raising its feathers so as to appear not unlike a puff ball; hence the general name they have received from the English residents in Brazil; of which vast country all the species, I believe, are natives. When frightened, their form is suddenly changed by the feathers lying quite flat; they are very confiding, and will often take their station within a few yards of the window; the two sexes are generally near each other, and often on the same tree. Total length rather more than eight inches; bill, one inch and three quarters from the gape, and half an inch less from the nostrils; it is very strong, thick, black, and slightly compressed; the tip of the upper bifid; the bristles at its base covering the nostrils are long and incurved, and those situated at the base, under the eye, very stiff; the upper part of the head black, the feathers much lengthened; the sides, front, ears, and forepart of the throat white, uniting at the back of the head into a narrow collar. The whole of the remaining plumage above is black, glossed with greenish; across the breast a black bar, which separates the white of the throat from the buff colour which tinges the abdomen and vent; the flanks are marked with dusky transverse stripes; the tail is slightly rounded and three inches and a half long, some of the feathers with a very fine line of white at their tips; all the quill feathers have the base half of their inner shafts white, as well as the greater covers inside, the lesser being black; legs and claws blackish. I am disposed to consider this bird only as a variety of the _Greater pied Barbut_ of Dr. Latham, differing in having the plumage on the under part of the body pale ferruginous, or buff colour, instead of white, as in the specimens he described from Cayenne; mine are from Southern Brazil, where the species is not uncommon. This genus includes the American species of the Linnaean Barbuts; the birds connecting this group with the cuckows are arranged by Vieillot in a separate genus, named by him _Monassa_; which I think should be retained, as it is of much importance to designate strongly connecting links between families apparently very opposite. * * * * * Pl. 100 [Illustration] XENOPS genibarbis, _Whiskered Xenops._ * * * * * GENERIC CHARACTER.