OCR Text |
Show 1881.] ANATOMY OF THE JAgANAS. 645 The drawing (fig. 2) of the sternum of Metopidius alBinucha will show how unlike it is to that of the Rallidae. In the latter group the sternum is always peculiar in that the xiphoid processes exceed in length the body of the sternum, which tapers to a point posteriorly, and from which they are separated by very long and well-marked triangular notches. The carina sterni also is less well developed; and the clavicles are weaker and straighter, being less convex forwards, than in the Parridae. The sternum and clavicles Fig. 2. Sternum and shoulder-girdle of Metopidius albinucha, viewed laterally; natural size. of Parra and Metopidius in general form, on the other hand, resemble closely the type found in some of the Pluvialine birds (e. g. Thinocorus, Attagis). # The pelvis, again, of the Rails presents certain well-marked peculiarities. If that of Rattus aquaticus be taken as a typical form, it will be found that the ilia are long and narrow, and but little expanded in their preacetabular part. The postacetabular portion of the pelvis is but little bent down on the preacetabular part; and the ischia and pubes are but little everted. The ischia are united by broad bony plates to about the three most posterior "sacral" vertebrae ; between these plates and the expanded part of the ilia above are well-developed and deep fossae, occupied, in the fresh state, by the posterior portion of the kidneys. Viewed from above, the well-marked "postacetabular" ridge, which divides off the dorsal from the lateral aspect of the pelvis, running from just behind the anti-trochanteric eminence to the posterior spine of the ilium, presents, a little behind those two points, a strongly projecting process. The greatest breadth of the postacetabular part of the pelvis is therefore here, and not at the more anteriorly-situated prominence close to the antitrochanter. Viewed from the side, this ridge forms a sort of overlapping roof to the slightly excavated external pelvic fossa. The genera Ocydromus, Aramides, Fulica, and Porphyrio do not essentially depart from this type. In Parra and Metopidius x the ilia are wider and more expanded 1 Milne-Edwards has also described the difference of the pelvis in the Jaganas as compared with that of the true Kallidaj: cf. ' Oiseaux Fossiles,' ii. p. 123. |