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Show 588 MR. H. O. FORBES ON BIRDS FROM [Dec 4, not make an ordinary web ; but only the thinnest film on the surface of the leaf. The appearance of the excreta rather recently left by a bird on a leaf is well known. There is a pure white deposit in the centre, thinning out round the margin, while in the central mass are dark portions variously disposed ; as the leaf is rarely horizontal, the more liquid portions run for some distance. N o w this Spider one might almost imagine to have in its rambles ''marked and inwardly discerned " what it had observed, and had set about practising the " wrinkles" gained ; for it first weaves a small irregular patch of white web on some prominent leaf, then a narrow streak laid down towards its sloping margin ending in a small knob; it then takes its place on the centre of the irregular spot on its back, crosses its biack-angled legs over its thorax, and waits. Its pure white abdomen represents the central mass of the bird's excreta, the black legs the dark portions of the slime, while the web above described which it has spun represents the more watery marginal part (become dry), even to the run- off portion with the thickened knob (which was not accidental, as it occurred in both cases), like the residue which semifluid substances ending in a drop leave on evaporation. It keeps itself in position on its back by thrusting under the web below it the spines with which the anterior upper surfaces of the legs are furnished. The most interesting fact of all to m e is, not so m u c h that of the Spider haviug gained, which it can, of course, have no consciousness of, by natural selection the colour and form of an excretum, but that it has acquired the habit of supplementing its own colour and form by an addition in such absolute harmony with that of which itself is the similitude. 4. O n a n e w Species of Thrush from Timor Laut, with remarks on some rare Birds from that Island and from the Moluccas. By H . O . F O R B E S , F.Z.S. [Received November 20, 1883.] (Plates LII. & LIII.) The specimen of Geocichla which I have now the pleasure of exhibiting (Plate LII.) is an adult male of a species intermediate between G. rubiginosa of Timor and G. erythronota of Celebes, two species which are also now represented on the table through the kindness of Mr. H . Seebohm. The general colour of the upper parts is olive-brown, shading into slaty brown on the head and into chestnut on the rump and upper tail-coverts; lores white, ear-coverts mottled white and slaty brown; wings brown; lesser wing-coverts olive-brown, broadly tipped with white; innermost secondaries russet-brown, obscurely tipped with white ; tail-feathers russet-brown, the outer feathers on each side broadly tipped with dull white; chin, throat, and breast buffish |
