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Show 1867.] PROF. HUXLEY ON THE CLASSIFICATION OF BIRDS. 455 the Plovers and their allies as the most central group of these birds, we may pass, without a break of more than family importance, along-several distinct series, or gradations, of ornithic forms. Thus, along one line, the Bustards are intermediate between the Plovers and the Cranes; while Psoqihia and Rhinochetus lead from the Cranes to the Rails. Following another line, Hemipodius stands between the Plovers and the Fowls; while Syrrhaqites inclines, on the one hand, to the typical Gallinaceous birds, and on the other to the Columbidce. A third series is commenced by the Gulls. The osteological resemblances between a Plover, a Gull, an Auk, and a Diver are so close that it is utterly out of the question to regard these Birds as members of different orders. But the Gulls grade insensibly into the Procellariidce ; and, though the Apterodytida; appear to be separated by a broad gap from the Alcidce, Alca impennis, in the form of its humerus, in the mode of articulation of the radius and ulna with the humerus, in the proportions and structure of the tarsometatarsal bone, shows itself to be an almost intermediate form. I am acquainted with only two birds, Dicholophus and Crax globicera, the structure of the skull of which would lead me to regard them as transitional between the Schizognathous and the Desmognathous sections, or, at any rate, as approaching the latter division. Nitzsch and Burmeister have assigned to Dicholophus a position near the Cranes and the Rails, and, no doubt, justly on the whole, though I venture to think that they have underrated the points of resemblance to the birds of prey, and especially to Gypog er anus. In the skull of Dicholophus the internasal septum is ossified to a very slight extent, and the maxillo-palatine processes may meet in the middle line, in both of which respects it approaches the birds of prey. But the ossified part of the nasal septum does not unite below with the maxillo-palatines; and in this respect Dicholophus is unlike the Raptorial birds*. Crax globicera, on the other hand, while it retains the characteristically Gallinaceous basipterygoid articular surfaces, palatine bones, angle of the mandible, and other peculiarities, has a partially ossified nasal septum, which divides below and unites with the maxillo-palatines, just as in the Raptorial birds. The Cuculidce and Alcedinidee occupy nearly the same middle place in the Desmognathous series that the Plovers have among the Schizognathous families. The Musophagidee bring them into relation with the Raptorial birds, the Rhamphastidee with the Parrots, the Podargidee with Cancromaf, and so with the Herons and Storks. But these last are clearly affined, on the one hand, with the Cormorants and Pelicans, on the other with the Flamingos, and through the latter with the Lamellirostres. * Mr. Parker is inclined to lay a still greater stress than I have done upon the many Raptorial characters of Dicholophus. f A hazardous suggestion, but one the temerity of which will perhaps appear less after a careful comparison of the skulls of these two birds. |