Ridgway — American Families of Oligomyodian Passer es. 11 



non-exaspidean. I am led to attach great value to this 

 character for the reason that no matter how great the variations 

 in general form or specialization of other characters within the 

 Tyrannidae and Pipridae the character of the tarsal envelope is 

 practically uniform throughout these groups. 



Tyrannid^. 



In order to get as clear an understanding as possible of the class- 

 ification of the Tyrannidse, all the genera available* have been 

 carefully examined and compared. Many days were devoted to 

 an attempt to construct a " key " to all the genera in hand, but 

 it finally became evident that the undertaking was much too 

 formidable for the limited time which could be devoted to it, 

 and tli^refore it became necessary to restrict the key to those 

 genera belonging to North and Middle America, together with a 

 few South American genera which were included for purpose of 

 comparison. Even with this elimination of half the genera the 

 task has proven exceedingly difficult and the results far from 

 satisfactory, although it is believed that some improvement has 

 been made over the ' ' purely provisional ' ' arrangement in 

 Vol . XIV of the ' ' Catalogue of Birds in the British Museum , ' ' 

 in which the so-called families are without question purely 

 artificial and the allocation of certain genera obviously wrong. f 

 The subject has called forth a very pertinent and interesting 

 paper by Dr. von Ihering,+ in which a partial reconstruction of 

 Dr. Sclater's " subfamilies," based on biological facts (chiefly 

 the character of nests and eggs), is shown to be necessary, the 

 proposed changes being as follows : 



(1) The Taeniopterinas restricted by elimination of the genera 

 Sayornis, Sisopygis and, probably, Machetornis . 



(2) The Platyrhynchinse divided into two groups, Euscarth- 

 minge and Serpophaginae. 



* The only genera not seen by me are Ochthomis Sclater, Cemtotriccus Cabanis, Pseudo- 

 triccus Taczanovvski and Berlepsch, Leptotriecus Cabanis and Heine, Pseudomyobius Sal- 

 vador! and Festa, Planchesia Bonaparte, Txniotriccus Berlepsch, Chxomyias Berlepsch, 

 and Acrochordopus Berlepsch and Hellraayr. 



t As an example may be cited the reference of one species of Sayornis (than which 

 there are fewif any more natural genera) to the "Tyranninse" and the remaining species 

 to the " Taeniopterinse," almost at opposite extremes of the arrangement ! 



I The Biology of the Tyrannidse with respect to their systematic arrangement. The 

 Auk, XXI, July, 1904, 313-322. 



