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Show 1892.] CLASSIFICATION OF BIRDS. 231 Of course this merely mathematical principle is scientifically faulty, because the characters are decidedly not all equivalent. It may happen that a great numerical agreement between two families rests upon unimportant characters only, and a small number of coincidences may be due to fundamentally valuable structures, and in either case the true affinities would be obscured. This it was necessary to inquire into. But at any rate I obtained many hints from this simple mode of calculation, indicating the direction which further inquiry should take. The Psittaci may serve as an example of m y mode of sifting characters. According to the numerical agreement of the 40 characters employed generally, we have the following table :- Psittaci agree with Coccyges in 31 points, with Pici in about 29, with Coraciidae 25, Falconidae 25, Striges 22, Bucerotidse 22, Gallidse 21, against 19 points of difference. A previous line of investigation had revealed the fact that the Coccyges and Gallidae are intimately connected with each other through Opisthocomus. This knowledge obviated further inquiry as to the affinity between Psittaci and Gallidae. I. Comparison of Psittaci with Falconidce. Psittaci and Falconidce agree. Nidicolous = Cuculi. Woolly nestlings. Distribution of nestling downs. Distribution of adult downs. Cervical apteria = Cuculi. Dorsal apteria = Coccyges. Ventral apteria = Musopkagidae. Aftershaft = Musoph. Tufted oil-gland = Musoph. Aquinto-cubital. Desmognathous = Cuculi. No basipteryg. proc. = Cuculi. Holorhinal == Cuculi. Nares iraperviae = Cuculi. Shallow temporal fossa. Number of cervical vertebrae = Cuculi. No spina interna = Cuculi. Spina externa = Cuculi. Posterior sternal margin = Cuculi. Coracoids = Cuculi. Furcula = Cuculi. Humero-coracoid groove = Cuculi. Cervical haemapophyses = Cuculi. 2 carotids = Cuculi. Tongue. Intestinal convolutions. Psittaci and Falconidce differ. Toes = Cuculi (not Pandion). 10 remiges = Cuculidae. No vomer = Musophagidas. Mandible = Musoph. + Ectepicondylar process = Cue. 4-Tibial intercondylar tubercle = Cuc. Hypotarsus complex = Cue. Flexor tendons = Cue. Garrod's formula = Cue. Large procoracoid process = Cue. Thoracal haemapophyses = Cue. Food - Musoph. Caeca none = Musoph. Syrinx specialized. 14 negative points. 26 positive points. cations within the various members of such groups, as, e. g., Tubinares and Accipitres, Limicolae and Passeres. These are traps which it is not always easy to avoid. |
