NATURAL SCIENCES OF PHILADELPHIA. G5 



b. var. irritabilis. 

 Tyr annus irritabilis, Vieillot, Ency. Meth. 1823, ii. 847, ex Suiriri pardoy- 



rojo, Azara, Apunt. ii. 143, No. 195. Paraguay. 

 Tyramiula irritabilis, Bp., C. A. i. 189. "Amer. Merid. Parag." 

 Myiarchus erythrocercus, Scl. et Salv., P. Z. S. 1868, 631, 632. Venezuela. 

 Myiarchus mexicanus, Lawr., A. L. N. Y. ix. 1869, 202. Yucatan. 

 Myiarchus yucata?iensis, Lawr., P. A. N. S. P. 1871, 235. Yucatan. 

 Pyrocephalus (Myionax) erythrocercus, Gr., H-L., No. 5522 (" crinitus p. 



Hart!.; irritabilis p. Bp. ; ferox %, Burm.") 

 Num Myiarchus mexicanus, Kaup, P. Z. S. 1851, 51 ? 



M. Myiarcho crinito ipsissimo simillimus, seel notaeo aliqu,antu- 

 lura obscuriore, gastrseo aliquantulum dilutiore, rectricibus rufo 

 et fusco fere dimidiatis ! rostro modico, nee crassitie M. cooperi pari. 



Habitat in America Centrali et Meridionali. Paraguay {Page; 

 avis Azarana-Vieillotiana ipsissima! Mus. S. I., No. 16,349). 

 Parana (Page; Mus. S. I., No. 16,348). Bahia (Mus. G. N. L. ; 

 spec, cum typo erythi-ocerci, Scl., comparatum et identicum esse 

 probatum). Venezuela (unde erythrocercus ipsiss.). Yucatan 

 (Mus. S. I. et Gr. N. L. specimina typica yucatanensis, Lawr., 

 1811 = mexicanus Lawr., 1869). Guatemala (Mus. G. N. L). 

 Costa Rica (Mus. S. I., No. 29,423). 



Obs. This bird, so far from being specifically distinct from the 

 ordinary North American form, is so extremely similar as to be 

 with difficulty recognizable as a variety of typical crinitus. The 

 size is the same; there are no evident nor constant differences in 

 the relative proportions of bill, feet, tail, and wings, and the general 

 colors only differ by a shade. The bill is exactly as in crinitus ; 

 having neither the elongate, constricted shape of cinerascens, nor 

 the general bulkiness of var. coojieri and of validus. In most of 

 my specimens it happens that the plumage is old and worn, so 

 that these look browner or grayer on the back than is usual for 

 true crinitus; but the Paraguay and Parana skins in better 

 feather are not to my eye an appreciable shade different from 

 several United States skins ; the yellow below, however, is recog- 

 nizably paler, and the gular ash seems to have a little more pectoral 

 extension. There is, however, one obvious and nearly constant 

 discrepancy in the pictura of the tail feathers, enabling me to 

 predicate a variety. On on average the rufous and the fuscous on 

 the inner webs of the rectrices are dimidiate half-and-half in 

 amount; this never occurs to my knowledge in United States 

 crinitus (cf. descr.). The relative breadth varies as follows: The 

 1872.] 



