192 Ridgway — Diagnoses of New Forms of Neotropical Birds. 



difficult to get together sufficient material to form a basis for such an 

 attempt, and I have been able to study the subject from material that is 

 only approximately adequate. The type locality of Lanius doliatus Lin- 

 naeus is Cayenne; and since the birds of this species from Venezuela, 

 Trinidad, and Tobago are recognizably different the name doliatus must 

 be restricted to those from the Guianas. In Colombia and eastern Panama 

 the range of tins species is completely interrupted. T. radiatus nigri- 

 cristatus (and T. radiatus albicans, if really distinct) entirely replacing 

 it, and it does not reappear until western Panama (Cbiriqui) is reached, 

 whence northward to the States of Tamaulipas and San Luis Potosi on 

 the eastern side and Chiapas on the Pacific side of Mexico the species 

 occurs throughout the hot and temperate zones. Notwithstanding their 

 wide geographic separation from their South American representatives, 

 T. doliatus doliatus of Cayenne, Surinam, and British Guiana and T. 

 doliatus fraterculus Berlepsch and Llartert,* of Venezuela, Trinidad, and 

 Tobago, some specimens from the Central American area closely resemble 

 one or the other of the two South American forms. On the whole, how- 

 ever, the Central American birds are obviously different; but owing to 

 the very considerable amount of individual variation among specimens 

 from almost any locality within the area designated it is very difficult to 

 make out geographic forms which can be satisfactorily characterized. The 

 average difference in coloration between specimens from the Atlantic and 

 Pacific slopes, respectively, is very marked, those from the former being 

 much darker, this darkness of coloration reaching its maximum develop- 

 ment in Honduras, where, however, most specimens are hardly if at all 

 distinguishable from the darker examples from eastern Mexico. In Yuca- 

 tan, however, the birds of this species are all light colored, resembling 

 those from the Pacific coast district much more closely than they do those 

 of Honduras and the eastern parts of Guatemala and Mexico. The differ- 

 ence in coloration between specimens from opposite sides of the continent 

 is much less marked as well as less constant in Costa Rica than in the 

 countries farther northward, many of those from the Pacific side being 

 quite as dark as some of those from the Atlantic side. 



In short, while puzzling exceptions to the general rule occur, it appears, 

 from the materia] examined, that three fairly definite geographic forms 

 of this species may be made out in Central America, two of which appar- 

 ently have not been named. These are 



( 1 ) Thamnophilus doliatus mexicanus Allen. Atlantic slope, from south- 

 ern Tamaulipas to Costa Rica, of winch T. intermedins Ridgwayt repre- 

 sents the dark extreme. Type locality, Jalapa, Vera Cruz. 



(2) Thamnophilus doliatus pacijicus Ridgway. Pacific slope, from 

 Chiapas to western Panama. (An earlier name for this may be Thamno- 

 philus rutilus Bonaparte, t described as from Guatemala; but it being 



*Nuvit. Zool., ix, no. 1, April 10, L902, 70 (type locality, Altagracia, Orinoco K.. 

 Venezuela; coll.Tring Mus.). 



T Proc. U. S. Nat. Mus., x, sig. 37, Aug. 6, L888, 581 (Truxillo, Honduras; coll. V. S. 

 Nat. Mus.). 



t Proc. Zool. Soc. Lond. ls::7. 117. 



