274 PROCEEDINGS OF THE NATIONAL MUSEUM vol.93 



The relationships and name for the birds in this collection have 

 been established only after a detailed study of all the woodpeckers 

 of this type found from Texas to Costa Rica. 



On first examination of this group of forms they appear a hopeless 

 jumble, but with study an orderly arrangement becomes evident. 

 The scheme here outlined in detail is that indicated by Griscom 32 

 except that it appears that veraecrucis is distinct rather than a 

 synonym of grateloupensis. 



After a somewhat prolonged study, it is evident that there are two 

 principal types of these woodpeckers. The first comprises those with 

 the dorsal surface boldly barred with black and white, and the abdo- 

 men yellow, including the three subspecies aurifrons, polygrammus, 

 and frontalis. The second has the white barrings decidedly nar- 

 rowed, so that with the black predominant the appearance is quite 

 different, this group covering the subspecies veraecrucis, dubius, leei, 

 santacruzi, pauper, canescens, and insulanus. I am inclined to believe 

 that the red abdomen found in typical veraecrucis, dubius, and leei 

 is the original condition, and that the yellow and orange-yellow of 

 the abdomen in santacruzi, pauper, canescens, and insulanus represent 

 a modification of this. I also think that the two general groups dis- 

 tinguished by difference in dorsal pattern have arisen independently 

 and that they have joined subsequently by merging at their points 

 of contact. The race grateloupensis is a present-day series of inter- 

 mediates between the two. On this thesis, the heavily barred group 

 may have had a more extensive former range from which it may 

 have been crowded in part by invasion of the other. This would 

 account for the present distribution, where there is apparently no 

 actual contact between aurifrons and polygrammus, though the sepa- 

 ration is for a small distance only, as well as for the far greater 

 separation of Centurus hoffmannii, which now is so different as to 

 rate treatment as a separate species. 



Following is a synopsis of the races of Centurus aurifrons ac- 

 cording to my present understanding of them : 



Centurus aurifrons aurifrons (Wagler) : 



Picus Aurifrons Wagler, Isis von Oken, vol. 22, pt. 5, May, 1829. col. 512 

 (Ismiquilpam, Hidalgo). 



Abdomen yellow; bands of white and black on dorsal surface 

 broad and heavy ; middle rectrices entirely black ; male, forehead yel- 

 low, crown patch red, nape orange; female, with crown gray. 



Birds from San Luis Potosi to Jalisco, i. e., those in the southern 

 part of the range, appear to have the black markings above some- 

 what heavier, but this is an indefinite tendency only. 



82 Bull. Amer. Mus. Nat. Hist., vol. 64, 10.°,2, pp. 220-230. 



