In the neighbourhood of Port Essington on the north coast, a species of this form is found which precisely resembles the present bird in every respect, except that it is about one-fifth smaller and has a rather larger bill; if these birds should ultimately prove to be merely varieties of each other, then the range of the species will be very extensive indeed; in my own opinion they are distinct, but whether I am right in thus believing or not, can only be ascertained by an increased knowledge of the productions of this vast continent. Mr. Gilbert states that the Port Essington bird is less abundant, less active, and has not so deep a voice as the _T. argenticeps_, but that the habits and manners of the two birds are precisely similar. The adult has the whole of the upper surface, wings and tail light brown; all the under surface pale greyish brown; bill and legs leaden olive; irides and eyelash nearly black; naked part of the face mealy bluish lead-colour. The young are similar to the adult, but have the feathers of the upper surface fringed with grey, and those of the wings slightly margined with greenish yellow; the throat and sides of the chest lemon-yellow; face blackish, and not so mealy as in the adult. The young of the Port Essington bird has the yellow colouring of the throat still more extensive than in the bird from New South Wales. The figures represent an adult and a young bird from specimens killed on the Namoi. [Illustration: ACANTHORHYNCHUS TENUIROSTRIS. _J. Gould and H. C. Richter del et lith._ _C. Hullmandel Imp._ ] ACANTHORHYNCHUS TENUIROSTRIS. Slender-billed Spine-bill. _Certhia tenuirostris_, Lath. Ind. Orn. Suppl., p. xxxvi. _Le Cap noir_, Vieill. Ois. Dor., tom. ii. p. 94. pl. 60. _Slender-billed Honey-eater_, Lath. Gen. Hist., vol. iv. p. 194. pl. lxii. _Flapping Honey-eater_, Lath. Gen. Hist., vol. iv. p. 195. _Hooded Creeper_, Shaw, Gen. Zool., vol. viii. p. 109. _Slender-billed Creeper_, Lath. Gen. Syn. Suppl., vol. ii. p. 165. pl. 129. _Meliphaga tenuirostris_, Vig. and Horsf. in Linn. Trans., vol. xv. p. 317. _Acanthorhynchus tenuirostris_, Gould, Syn. Birds of Australia, Part II. —— _dubius?_ Gould in Proc. of Zool. Soc., Part V. p. 25; and in Syn. Birds of Australia, Part II. _Cobbler’s Awl_, Colonists of Van Diemen’s Land. _Spine-bill_, Colonists of New South Wales.