REMARKS ON THE AVIAN GENUS MYIARCHUS, WITH SPECIAL 

 REFERENCE TO M. YUCATANENSIS LAWRENCE. 



BV 



Robert Ridgway, 



Curator of the Department of Birds. 



The discrimination and identification of tbe ypecies and geographical 

 races of the genns Myiarchus is one of the most difficult tasks with 

 which the student of Neotropical ornithology has to deal, the style of their 

 coloration being remarkably uniform, the species numerous, and their 

 geographical variations perplexing. Some forms once considered specif- 

 ically distinct, and indeed very different from one another when speci- 

 mens from distant areas are compared, are connected by intermediate 

 specimens where their respective ranges come together; in some cases 

 (as for example that of M. cinerascens and ill. nuttingi) it is not at all 

 improbable that hybridism plays a part and thus complicates the 

 problem; but in others {c. {/., M. mexicamis and M. magister) the inter- 

 gradation is on too extensive a scale to warrant serious consideration 

 of hybridism as the probable cause. 



Most writers are agreed as to the limits of the genus, the only species 

 involved in a difference of opinion regarding this point being the 

 M. harbirostris (Sw.), of Jamaica, which some of the best authorities 

 have referred to the Antillean genus Blachm, though I fail to dis- 

 cover wherein it differs structurally or otherwise (except specifically) 

 from the ^at-hilled Myiarchi {M. lawrencii and allies). Doubt has been 

 expressed by Messrs. Salvin and Godman {Biologla Centr all- Ameri- 

 cana., Aves, II, pt. 12, March, 1889, p. 96) as to the propriety of referring 

 M. Jlammulatus Lawr. to the genus Myiarchus, and in this doubt I 

 share so strongly that I have no hesitation in formally separating it. 

 (See p. 600.) Another species also seems to me to require separation 

 on account of its very long tarsi. This is the M. magnirostris (Gray), 

 of the Galapagos archipelago, a species which otherwise resembles the 

 smaller flat-billed species, though differing in having the bill much 

 narrower and less contracted at the tip. These two eliminations, 

 together with that of the fiat-billed group typified by M. tuberculi/er 

 and including M. laicreneii and allies, make four well-defined groups 



Proceedings National Museum, Vol. XVI— No. 955. 



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