Adults have the patches above the eyes, a semilunar mark at the back of the head, a band round the neck, and all the under surface grey, finely sprinkled with black, and tinged with buff; ear-coverts reddish buff, the remainder of the head blackish brown; all the upper surface and wings dark brown, sprinkled with grey in the form of irregular bars; primaries brown, sprinkled on their outer webs with lighter brown and grey; tail dark, regularly barred with numerous narrow lines of grey sprinkled with black: irides hazel; feet flesh colour. In immature birds the lunulate markings are much richer in colour and more distinct than in the adults, in many of which they are nearly obliterated, and the irides are nearly black. The figures are of the natural size. [Illustration: ÆGOTHELES LEUCOGASTER: _Gould_. _J. Gould and H. C. Richter del et lith._ _C. Hullmandel Imp._ ] ÆGOTHELES LEUCOGASTER, _Gould_. White-bellied Owlet Nightjar. _Ægotheles leucogaster_, Gould in Proc. of Zool. Soc., June 25, 1844. This is altogether a larger and more powerful bird than the _Ægotheles Novæ-Hollandiæ_; besides which, the white colouring of the lower part of the belly will at all times serve to distinguish it from that species. It is rather abundant on the Cobourg Peninsula, where it inhabits the forests in the immediate vicinity of Port Essington; how far its range may extend is at present unknown, but it is probable that the bird is distributed over the whole of the northern portion of the continent, and that it there forms the representative of the _Æ. Novæ-Hollandiæ_, which up to the present time has only been found on the southern. Mr. Gilbert states that it is abundant in most parts of the settlement at Port Essington, “where it is frequently seen flying about at twilight, and occasionally during the day. On the approach of an intruder it flies very heavily from tree to tree, and on alighting invariably turns round on the branch to watch his approach, moving the head all the time after the manner of the Hawk tribe.” The sexes when fully adult will not I expect be found to differ in plumage. I attribute the redness of some of my specimens to the age of the individuals; but whether the red varieties or the grey are the most mature birds, I have not had sufficient opportunities of ascertaining. It feeds on insects of all kinds, and as the bird is strictly nocturnal in its habits, they are, as a matter of course, procured at night.