1898.] NATURAL SCIENCES OF PHILADELPHIA. 489 



OBSERVATIONS ON THE CLASSIFICATION OF BIRDS. 1 

 BY DR. R. W. SHUFELDT. 



In former papers of mine the classification of various groups of 

 birds has been treated ; their osteology, as a rule, being the anatom- 

 ical system employed and referred to for the purpose. These inves- 

 tigations, as many are aware, have not been confined entirely to 

 recent avifaunse, but have also taken into consideration fossil 

 material ; the remains of birds that existed as far back as tertiary 

 time. 



So far as the United States ornis is concerned every family, or 

 indeed, nearly every genus of the recent age has thus been dealt with, 

 and some of the mss. presenting the details of these researches have 

 been published, while the far greater proportion of them tempora- 

 rily await a similar disposition. It is in this manner that such groups 

 as the Passeres, the Swifts, the Humming-birds, the Goatsuckers, the 

 Trogons, the Kingfishers, and many others have been gone over and 

 issued in the form of memoirs in different publications, while upon 

 the other hand the osteology of entire groups has been written out 

 and illustrated, and will, when printed, fill in gaps that formerly 

 existed. Among these last, extensive work has also been done with 

 large and small groups of birds not occurring in this country, as the 

 Penguins, the Ostriches, and others. These will not be taken espe- 

 cially into consideration in the present connection, for the reason 

 that considerable unanimity of opinion exists among naturalists 

 with respect to their taxonomy ; though probably the Penguins form 

 an exception to this statement. Commencing in the United States 

 avifauna with the Pygopodes, however, and passing the various 

 groups in review following their linear arrangement in the order in 

 which they are usually printed, we meet not only with single species 

 but with groups of species, the true taxonomic position of which, in 

 the system, ornithologists entertain very diverse opinions. It 

 is to these that it is my intention to refer in the present paper. 

 They have all been closely studied by me osteologically, and in the 



1 Read by title at the Sixteenth Congress of the American Ornithologists' 

 Union, at the United States National Museum, Washington, D, C. 17th of 

 November, 1898. 



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