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Show 1881.] ANATOMY OF THE JACANAS. 641 is a muscular gizzard, lined by a rather thick and hard epithelium. The contents of the stomach, in one of the specimens examined, consisted of small seeds mixed with vegetable debris and small fragments of stone. The right liver-lobe is elongated, and twice as large as the left; and there is a well-developed gall-bladder. The caeca are lateral in position, and closely approximated to the intestine, which makes them difficult to see. They are mere nipples '2 inch long l. In this respect Parra differs from all the Rallidae (except Porzana notata) which have been examined, as in all of these the caeca are long, sometimes very long. Of the Pluvialine birds, only the Plataleidae and Rhinochetidae, with Sterna, Larus, and one or two others, have such short caeca. The intestines measure, in these two specimens of Parra jacana-small intestine 12*3 and 13*2 inches, large intestine 1*1 and 1*0 inch respectively. In Parra jacana and in Hydrophasianus africanus, as also in Metopidius africanus, as already recorded by Garrod2, there are two carotid arteries. This is the number found in all the Rallidae, and in most of the Pluviales, excepting the Turnicidae and Arctica alle, according to Garrod3, where there is only the left developed. Myology. Parra jacana resembles P. (Metopidius) africana, as recorded by Garrod 4, in possessing the ambiens, femoro-caudal, accessory femoro-caudal, semitendinosus, and accessory semitendinosus muscles, all well developed5. Their formula is therefore A B . X Y 6 . In both these species the gluteus primus is well developed, covering the biceps superficially towards the median line; the gluteus quintus is also well developed. As in the Rallidae, and the Gruidae7 and Eury-pyga, amongst the Pluviales, the area of origin of the obturator internus is triangular, as it is also in Hydrophasianus; in the Pluvialine birds generally it is oval. The two deep flexor tendons of the foot are not at all ossified, but completely blend together some way up the leg-in Metopidius, in fact, just below the joint. There is no slip at all to the hallux, as was also found to be the case in Parra africana8 and Hydrophasianus by Prof. Garrod. This is the more remarkable on account of the very large size of the hallux in all these birds. A special tendinous slip to that digit is very frequently present in birds which have a very insignificant hallux indeed ; and I know of no other case of a bird with such a large hallux as that of the Parridae lacking the tendon. This fact would seem to indicate that the Parridae may have been developed from some form with a more normal-sized foot and a small hallux, which had no 1 In Hydrophasianus chirurgus there is a strong gizzard, and the left liver-lobe is smaller than the right; the caeca measure '15 inch, the whole length of the intestines being 12 inches.-Garrod's MSS. 2 P Z S. 1873, p. 469. 3 L. c. pp. 469, 470. * P. Z. S. 1873, p. 641. 5 In Hydrophasianus all these five muscles are also present. e Cf. Garrod, P. Z. S. 1874, p. 123. 7 Garrod, P. Z. S. 1876, p. 199. s P. Z. S. 1875, p. 348. |