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Show 1886.] CUBITAL COVERTS OF BIRDS. 193 with any conspicuously-marked Pigeon of the normal type (Columba guinea, for example, fig. 14 a) on the other. The difference, to me, appears both striking and significant. Perhaps I may be allowed to remark that the characteristic differences between Goura and the normal Pigeons are represented in the very useful series of coloured illustrations now posted up outside the Western Aviary in the Society's Gardens. In addition to the difference already noted between the true Pigeons and Goura, the following points of agreement and of difference between the two groups may be considered : - In the normal Pigeons an oil-gland is present; but is absent in Goura. In the normal Pigeons the tail-feathers are 12 in number ; while there are 16 in Goura. In the normal Pigeons the pterylosis is columbine ; and is galline in Goura. In the normal Pigeons caeca are present; but are absent in Goura. In the normal Pigeons a gall-bladder is present: no gall-bladder in Goura. In the normal Pigeons incubation lasts 16 days; but extends to 28 days in Goura. In addition to these peculiarities reference may be made to the bird's pheasant-like habits, to certain peculiarities of the urosacral and of the caudal vertebrae, to the number of the cervical vertebrae, to the absence of pterygoid processes, and to other features referred to by Prof. Huxley (P.Z.S. 1868, p. 302) and by Prof. Parker (T. Z. S. v. p. 151, 1863). Dr. Sclater (Ibis, 1880, p. 407) refers to certain peculiarities of the tarsus, in addition to the differences just noted, as evidence in favour of separating Goura from the Pigeons. The main differences that distinguish the wing of the Peristeropod Gallinaefrom that of the Birds of Prey have already been pointed out. It remains to add that the prominence of distal overlap introduced by Talegalla^ Crax and its allies, becomes more accentuated in Numida, and thence, through the Tetraonidae (fig. 15, p. 194), reaches its greatest development amongst the Gallinae in the typical Pheasants. A progressive increase of distal imbrication can be traced, in the first stages, only in the first, or posterior, row of median coverts, then in the second, and the third, and so on, until in Polyplectron all the more conspicuous feathers in the closed wing of the living bird seem to lap from the proximal towards the distal side of the wing. Excellent examples of the features referred to may be easily observed in the Society's Pheasant Aviary, where Lophophorus impeyanus, Euplocamus swinhoii, Phasianus reevesi, and Polyplectron chinquis well display the feature referred to. A reference to the annexed figure of Euplocamus swinhoii (fig. 16, p. 194) will serve to make the general disposition clear. Pavo follows a slightly different pattern ; and it is a point worth |
