482 DR. J, MURIE ON THE DERMAL AND VISCERAL STRUCTURES 
are sufficient for my purpose; and by describing one I include the other, so nearly 
identical are they. 
Ducorps’s Cockatoo’, Cacatua ducorpsii, Hombr. et Jacq., is that which I have illus- 
trated (Pl. LVI. fig. 11); the other, the Grey Parrot, Psittacus erithacus, I intercalate 
in the text. In the first cited every short, dumpy, powder-down feather is unequivocally 
distinct and full of dust, the larger rump-plumes being en masse; all are white. The 
second species has smaller and darker-coloured feathering, so that the rough definition 
is less salient and striking when the contour-feathering is removed. 
Upon the back of the head and neck small, delicate, single-rooted, and promiscuously 
scattered powder-down feathers obtain (see fig. 11, CV) equivalent to a cranio-nuchal 
patch. 
Lateral neck-patches are absent in €. ducorpsii, but foreshadowed in P. erithacus 
by only a few strong featherlets. 
Clavicular and breast-pufts (7. e. furcular coracoid) and pectoral portion of lateral 
sterno-ventral patches are met with in the latter bird, but not in the former. They are 
small, short, and rather separately dispersed. 
In the Cockatoo two or three featherlets may be recognized on the alar membrane, 
humeral alar (II, fig. 11); none are distinguishable in the Parrot. 
The dorsal patches in both species are in greater profusion (D’, D’, and D” in fig. 11); 
and the caudal bunch of long plumes cannot be mistaken. 
No manifest costo-thoracic or fenoral patch is discernible in P. erithacus; but both 
are sparsely represented in C. ducorpsii (C.T' and F). 
In the Grey Parrot’s groins and front of tibia, as far as its middle, scattered pens 
obtain; I did not specially note them in Ducorps’s Cockatoo, although they may be 
present. Such last powder-feathers indicate tendency to crwral and gastric portions of 
lateral ventral patches. 
Of whatever importance as an item of affinity may be the development and distribu- 
tive amount of powder-down patches among families of birds, it certainly has less 
weight as evincing relationship betwixt the higher orders, For example, we should 
hardly be prepared to admit it as a strong bond uniting such genera of the Gralla and 
Psittaci as possess it with the widely different Accipitres, several of which Nitzsch has 
shown have more than a fair sprinkling. Moreover its isolated presence in single 
species and genera of Passerine (Ocypterus), Gallina (Tinamus), Picarie (Podargus and 
Leptosoma*) forbids the idea. 
Let us for a moment glance pterylographically at the powder-downs in these diverse 
groups. Those beautiful plumose clumps on the rump of the Podargus and Green 
Leptosoma evidently consist of a posterior remnant of the lengthened dorsal patch in 
' A specimen of this rare form is delineated in our ‘ Proceedings,’ 1864, pl. xvii. 
* Dr. Sclater is inclined to regard the Leptosoma discolor as structurally approximating to the Coraciide more 
than to theCuculide, This bird has prominently a pair of ilio-dorsal powder-patehes,—P. Z. 8. 1865, p. 686, fig. 5. 
