Crown of the head, back of the neck, throat, abdomen, thighs and under tail-coverts white; feathers of the chest mottled with brown, and with a dark brown mark down the centre; ear-coverts and sides of the neck dark brown; back, wings and tail clove brown, each feather of the back with a narrow circle of white at its extremity; primaries black; bill black; cere and base of the bill bluish lead-colour; feet pale bluish white; irides primrose-yellow in some, bright orange in others; claws black. The figure is about two-thirds of the natural size. [Illustration: FALCO HYPOLEUCOS: _Gould_ _J. Gould and H. C. Richter del et lith._ _Hullmandel & Walton Imp._ ] FALCO HYPOLEUCUS, _Gould_. Grey Falcon. _Falco hypoleucus_, Gould in Proc. of Zool. Soc., Part VIII. p. 162. _Boorh-ga_, Aborigines of Moore’s River in Western Australia. Of this rare and beautiful Falcon I have seen only four examples, three of which are in my own collection, and the fourth in that of the Earl of Derby. The specimen from which my description in the “Proceedings of the Zoological Society” was taken, was presented to Mr. Gilbert by Mr. L. Burgess, who stated that he had killed it over the mountains, about sixty miles from Swan River; subsequently it was obtained by Mr. Gilbert himself in the vicinity of Moore’s River in Western Australia; and my friend Captain Sturt had the good fortune to secure a male and a female during his late adventurous journey into the interior of South Australia. “They were shot at the Depôt on a Sunday in May 1845, just after service; they had been soaring very high, but at length one descended to the trees on the creek, and coming within range was shot; when the other proceeding to look after its companion was also killed. It must be a scarce bird, for no others were seen.” The acquisition of the _Falco hypoleucus_ is highly interesting, as adding another species to the true or typical Falcons, and as affording another proof of the beautiful analogies which exist between certain groups of the southern and northern hemispheres; this bird being as clearly a representative of the Jerfalcon of Europe, as the _Falco melanogenys_ is of the Peregrine, and the _Falco frontatus_ of the Hobby; but as I have more fully entered into this subject in my observations on the genus, it is unnecessary again to detail them here.