Nelson North American Mainland Myiarchus. 27 



The authors of the Biologia however, in place of using. Baird's 

 name cooperi unite the birds of eastern and western Mexico 

 under Ridg way's mayister, which is a distinct subspecies from 

 cooperi and should not be confused with either of Kaup's 

 birds. 



The color terms in this paper are based on Mr. Ridgway's 

 'Nomenclature,' and all measurements are given in millimeters. 



I have again to thank Mr. Robert Ridgway and Dr. Chas. 

 W. Richmond, of the National Museum, for their continued 

 courtesies. 



KEY TO SPECIES AND SUBSPECIES. 



Bill rounded, with depth at angle of gonys nearly or quite equal to 



width at same place (subgenus Myiarchus) 



Wing and tail feathers without rufous or cinnamon area on either web; 



crown olive brown; back greenish olive - panamenais p. 29. 



Wing and tail feathers with distinct rufous or cinnamon area on one 



or both webs 



Inner web of outer tail feather usually entirely rufous (except in 

 some specimens a narrow dusky line along shaft mainly near 

 tip) 

 Bill small and proportionately slender (exposed culmen usually 



less than 19 mm.) 



Size small, wing usually less than 86 mm. - nuttingi p. 37. 

 Size larger, wing usually more than than 93 mm. ( 9 's in part) 



cinerascens p. 33. 

 Bill stout and proportionally heavy (exposed culmen usually more 



than 19 mm.) 



Underside of neck and breast pale ashy gray braehyurus p. 40. 

 Underside of neck and breast dark gray 



Exposed culmen not over 20 mm. - - crinitus p. 29. 



Exposed culmen over 20 mm. * residuus p. 30. 



Inner web of outer tail feather partly or wholly dusky 

 Inner web of outer tail feather wholly dusky yucatanemis p. 41. 

 Inner web of outer, tall feather partly dusky 

 Inner web of outer tail feather with well defined dusky band 



along shaft, rufous along inner border to tip 

 Bill long and heavy (usually 20 mm. or over); dusky band on 

 inner web of outer tail feather usually broadest in mid 

 dle. 



Size smaller, wing usually less than 105 mm. mexicaniLs p. 31. 



Size larger, wing usually more than 105 mm. magister p. 33. 



Bill small and slender, exposed culmen usually less than 18 



mm.; dusky band on inner web of outer tail feather 



broadening gradually from base, widest at tip 



