OCR Text |
Show 642 MR. W. A. FORBES ON T H E [May 17, special long flexor, the great size of their feet having been developed in accordance with their peculiar habits. In the anterior extremity the second pectoral arises from nearly the whole length of the sternum ; in all three genera the third pectoral is wanting. The expansor secundariorum is strong and T-shaped, as in all Balline and many Pluvialine birds. In Parra jacana (as in Hydrophasianus, according to Garrod) there is a distinct biceps slip to the patagium, as in all tbe Rallidae, the Chara-driidae, Gruidae, and many other Pluvialine birds. In Metopidius africanus it is apparently absent, the absence being probably correlated with the peculiar expanded form of the radius (to be hereafter described). In the wing-membrane the tensor patagii Brevis presents a peculiar arrangement, the tendon being completely divided into two portions- an inner, more slender, and an outer, stronger one. The former runs on to the fibrous tissue near the superficial origin of the extensor metacarpi radialis longior, and there stops ; the latter continues over this last muscle to the ulnar side of the arm, where it is lost in the fibrous covering-tissue adjacent. Before crossing, however, it sends off a short, special wristward slip to the superficial tendon of origin of the metacarpal extensor, as in many other groups of birds. There is also a thin fibrous expansion given off just before this to the tendon of the tensor patagii longus, and the tissue of the patagium generally, as in many Pluvialine birds 1. This splitting up of the tensor patagii Brevis tendon into two distinct slips, the external one in turn giving off a special wristward slip, occurs in many Pluvialine birds (e.g. in Numenius arquatus, Totanus calidris, 3fa-chetes pugnax, Himantopus nigricollis, Thinocorus, and Attagis), but never in the Rails, where the tendon is always much more simple, not being divided into two separate parts, or giving off a wristward slip. In fact, in most Rallidae it runs quite simply, as a narrow straight tendon, onto the origin of the extensor metacarpi muscle, and there stops. The trachea is provided with the usual pair of sterno-tracheal muscles; and the lower larynx, which is of simple structure, has also only a single pair of intrinsic muscles. Osteology. From a consideration of the pterylographic, visceral, and myolo-gical features only of the Parridae, perhaps no very definite conclusion as to their affinities could be drawn. But their osteological characters, in this case, leave no doubt as to their real position. All the skulls of Parridae which I have examined, including those of Parra? jacana and gymnostoma, Metopidii indicus, africanus and albinucha, and Hydrophasianus chirurgus, like that of Hydralector cristata figured by Garrod 2, are strongly schizorhinal, therein differing completely from that of the Rails, and resembling that of the 1 In Hydrophasianus much the same arrangement of the tensor patagii brevis obtains, to judge from a small drawing in Garrod's M S . 2 P. Z. S. 1873, p. 34, fig. 5. |