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Show 1890.] ANATOMY OF PODICA SENEGALENSIS. 433 He does not, however, direct attention in the skull to all the points which I refer to in the following brief enumeration of the characters which distinguish the Grebe from the Rails. In the Rails the maxillo-palatines are large, and are not concealed by the underlying palatines when the skull is viewed from below \ In the Grebe, the maxillo-palatines are very slight curved plates of bone, which are almost entirely concealed by the underlying palatines, only projecting very slightly on the inner side of these bones. In the Rails the cranial axis extends as far forward as (at least) the middle of the maxillo-palatines. In the Grebes it does not reach the posterior margin of these bones. Fig. 2. Skull of Podica senegalensis, lateral view; nat. size. In the Rails the temporal fossa is not bounded by very sharply marked ridges2; in the Grebes it is so marked, particularly in Podiceps cornutus and P. cristatus; in P. minor this character is less obvious. The temporal fossce themselves are much more extensive in the Grebes than in the Rails. The occipital condyle in the Rails is round; in the Grebes it is decidedly kidney-shaped with the " hilum " above. The forward process of the quadrate3 is more slender in the Grebes than in the Rails. The general outline of the skull from above appears also to be very characteristic in these two groups. The hinder part of the skull is rhomboidal in the Grebes, and squarish in the Rails ; this is due to the peculiar development of the temporal fossae, which are quite visible from above, while the jutting-out region of the skull 1 In the shape of its maxillo-palatines, Fulica comes nearer to Podiceps than do either Ocydromus or Crex ; they are curved and comparatively thin in Fulica, instead of being inflated bullae as in the two latter genera. 2 In Ocydromus australis this ridge is rather more marked than in Fulica, Crex, and Aramides; it is curious to note there is not any approximation here to the Grebes through P. minor. In the Rail it is the commencement of the ridge which is best marked, in the Grebe the middle portion. Giebel has remarked that Podiceps minor is less of a typical Grebe than is, for example, Podiceps cristatus; but he does not refer to this particular point. 3 Special attention has been lately directed to the quadrate as furnishing evidence of particular affinities in an interesting paper by Miss Walker (Studies from the Mus. of Zool. Univ. Coll. Dundee, vol. i. no. 1). |