Todd — Studies in the Tyrannidoe. 183 



cated the true systematic position of some of the South Ameri- 

 can forms in deahng with the North American members, while 

 Mr. Hellmayr and the late Count von Berlepsch have made 

 sundry contributions to the subject. 



In the key which follows Myiarchus semirufus Sclater has not 

 been included. This species has recently been made the type 

 of a new genus, Muscifur, by Messrs. Bangs and Penard. 

 Every one of the diagnostic structural characters claimed for it 

 by these authors we find repeated in typical Myiarchus, leaving 

 only the different color-pattern to be considered, and an 

 additional character in what appears to be the rougher scutella- 

 tion of the tarsi. Whether under the circumstances Muscifur 

 deserves recognition is an open question. Probably it would be 

 better to keep its type in Myiarchus in spite of its aberrant 

 coloration. 



Key to the South American Forms of Myiarchus. 



A. Rectrices with more or less cinnamon. 



a. Throat and breast pale neutral gray; posterior under parts 



brighter yellow ...Myiarchus crinitvs. 



a'. Throat and breast pallid neutral gray; posterior under parts paler 

 yellow {Myiarchus tyrannulus) . 

 b. General coloration darker; upper parts more grayish. 



c. All the rectrices except the middle pair with broad inner 

 margins of cinnamon, sharply defined from the brownish 



area — - Myiarchus tyrannulus tyrannulus. 



c'. Outer rectrices with little or no cinnamon, and the cinna- 

 mon color not sharply defined on any 



Myiarchus tyrannulus bahioe. 

 h'. General coloration paler; upper parts more greenish 



Myiarchus tyrannulus pallescens. 

 A'. Rectrices without cinnamon (except sometimes as a narrow external 

 edging), 

 a. Larger forms; wing of male averaging not less than 90 mm., of 

 female not less than 85 mm. 

 b. Pileum not strongly contrasted with the back, 

 c. Rectrices without conspicuous paler tips. 



d. Tail relatively shorter, approximately nine-tenths of 

 the wing; outermost (tenth) primary relatively 

 longer, exceeding or only slightly shorter than fourth ; 

 bill weaker and lighter colored, 

 e. Above lighter, more olivaceous. 



f. Above paler (Saccardo's olive); breast more 

 strongly contrasted with abdomen 



Myiarchus pelzelni. 



