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Show 1889.] CONVOLUTIONS IN BIRDS. 311 back, and especially the terminal end of the second resembles somewhat a plagioccelous formation. The Pteroclidae have consequently various points in common with several ratherdiversegroups; theyagree with the Rallidae in having the 2nd and 3rd loops left-handed, but differ from them and from the Limicolae in having all the loops closed. They differ from the Rallidae and agree with the Columbae and lower Limicolae in the number of loops. All this tends to indicate that the Pteroclidae have branched off from the common Gralline stock before the separation of the latter into Limicolae and Rallidae had taken effect, and before either typical Columbae or Gallinae were developed. That they have, in the diagram, to be placed in the isoccelous circle-which really belongs to totally different birds- shows also that they have made an early and special departure. The Alcidce are periccelous and strictly orthoccelous ; they agree with the Laro-Limicolae in the configuration of their first three loops, but they differ from them in the number of loops, which is at least six, the last three of which are left-handed. The Alcidse seem to have started from some low Limicoline forms and to have branched off early into a strictly orthoccelous direction. They are, in this respect, further removed from the Laridae (least so from the Terns), and render the term Gaviae somewhat vague. They approach the Pggo-podes (Colymbidae and Podicipitidae). The Colymbidae show unmistakable affinities with what may be called generalized or low Gralline forms ; their five loops are closed, orthoccelous, and alternating. The Podicipitidae differ somewhat from the Colymbidae, and besides possessing some special peculiarities, approach the Grallae more closely than do the Colymbidae ; at the same time in the possession of a pyloric dilatation they have a feature in common with certain Fulicariae and with the Steganopodes and Herodii. A peculiar resemblance also exists between Podiceps and Podica in the widely open and irregularly shaped last intestinal loop. AH this assigns a lower position to the Podicipitidae than to the Colymbidae, and gives them unequal rank, although the validity of the name Pygopodes can be maintained. They connect the large Gralline group with the following congregation, of which the Herodii, Steganopodes, Tubinares, and Spheniscidae are all divergent types. A very close connection exists between the Llerodii and the Steganopodes, and this is supported by numerous other characters. The Tubinares are in more than one respect the most specialized outcome of this great collective order, and reach in the typically mesogyrous Proceilariinee their highest development; whilst Puffinus and Diomedea are more generalized, and Ossifraga takes up a somewhat intermediate position. There are, in this respect, striking resemblances, of uncertain value however, with the Laro-Limicolae ; and thus we arrive at the same conclusion as Fuerbringer, who assigns to the Tubinares a position somewhat intermediate between but rather distant from the Laro-Limicolae and Steganopodes. The Spheniscidee are now a very specialized group. They possess undeniable characters in common with the Pygopodes, Steganopodes, and Tubinares; they are on the whole orthoccelous, but the 21* |
