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Show 18S2.J ANATOMY O F A N AUSTRALIAN D U C K . 457 the duplicature of the franum lingua1. On opening the mouth, the tongue being forced up against the roof of the mouth as is depicted in fig. 2, there is seen at its base, some way behind the level of the basihyal, a small circular aperture, about the size of a pea, lying between the two folds of the franum, the left of which is much stronger and better developed than the right. This aperture is the mouth of a small pouch, almost large enough to receive the end of the little finger, which extends backwards for some little distance to the base of the tongue, its breadth being nearly as great as that of that organ. This pouch is lined by mucous membrane of similar character to that found over the adjacent parts of the mouth ; its anterior limit extends forwards as far as the posterior end of the curious wattle attached to the lower jaw ; but there is no connexion between the two, the wattle being merely formed by a fold of the integuments, with no cavity contained in it. The observations hitherto made on the habits of Biziura in its native state fail to throw any light on the use or raison d'etre of this curious structure, though, judging from analogy, it is nearly certain that it is in some way connected with display during sexual excitement, and therefore confined, as we know the wattle is, to the male sex. The first specimen I examined had, I may remark, the pouch less developed than in the second one, probably an older bird. It is not improbable that further observations may show that, in thoroughly adult and breeding birds, this pouch acquires much greater dimensions than was the case in these two specimens. As regards other points, Biziura is in most of its features thoroughly Anatine. The tongue is quite duck-like, though very broad. There is a well-developed penis of the peculiar type found in other Anatidae. The number of remiges is 28, of which ten are, as usual, primaries. The pollex bears a small claw. There are 24 rectrices, a number not exceeded in any of the Anseres, though found in certain Swans. All are peculiarly stiff and curved, with flat lamellar rhachises. The caeca are long, measuring 6*75 and 7'7^> inches respectively in the two specimens. The ambiens muscle is large, and peculiar in that its tendon perforates the large-sized triangular patella, just as it does in Phalacrocorax and the extinct Hesperornis. The carina sterni is shallow, as might have been expected in a bird with such weak powers of flight as Biziura has. There is a minor myological peculiarity in the hind limb of Biziura, such as I have not yet observed in other Anserine birds. In all these the flexor longus hallucis and flexor profundus digitorum blend together towards the lower part of the tarso-metatarse, a comparatively very insignificant tendinous slip being given off from the tendon of the first-named muscle to the hallux before it blends with the other2. In Biziura the two tendons completely blend, but the small tendinous slip, given off, as usual, before they unite, does not go to the hallux as it normally does, but continues down to the bottom of the bone, and is there lost on one of the annular masses of fibro-cartilage 1 Murie, P. Z. S. 1869, p. 140; and Garrod, Coll. Papers, p. 245. 2 Garrod, Coll. Papers, pp. 293 and 298. 31* |
