224 FORMICARIIDZ. 
determined ; on the eastern side of the range the allied form, G. chiroleuca, takes its 
place. 
The female of this species was described by Mr. Lawrence as Myrmeciza ferruginea ®, 
as was pointed out by Sclater and Salvin in 1864 in their paper on M‘Leannan’s 
collections °. 
2. Gymnocichla chiroleuca. 
Gymnocichla nudiceps, Moore, P. Z.8. 1859, p. 55°; Scl. & Salv. Ibis, 1859, p. 119°; Lawr. Ann. 
Lyc. N. Y. ix. p. 109’. 
Gymnocichla chiroleuca, Scl: & Salv. P. Z. 8. 1869, p. 417*; Salv. Ibis, 1869, p. 314°; Scl. Cat. 
Birds Brit. Mus. xv. p. 272°; Ridgw. Pr. U.S. Nat. Mus. xiv. p. 469”. 
Precedenti similis, sed tectricibus alarum majoribus late albo marginatis, tectricibus minoribus externe omnino 
albis, plaga dorsali alba minore et nucha plumosa distinguenda. (Descr. exempl. typ. ex Tucurriqui, 
Costa Rica. Mus. nostr.) 
2 supra schistaceo-brunnea, capite summo et cervice postica saturate ferrugineis; alis fuscis extus obscure 
ferrugineis, tectricibus omnibus nigricantioribus et late rufo terminatis: subtus late ferruginea. 
¢ juv. femine similis, sed capite supra obscuriore, tectricibus alaram majoribus haud rufo terminatis. (Deser. 
femine et maris juv. ex Santa Ana, Honduras. U.S. Nat. Mus.) 
Hab. Honpuras, Omoa (Leyland 4), Santa Ana ( Wittkugel) ; Costa Rica, Tucurriqui 
(Arcé 4). 
Though only two male specimens are known to us, this bird is evidently distinct 
from G. nudiceps. Not only are the wing-coverts much whiter, but the denudation of 
the head is not carried nearly so far back as in the allied species. This fact is of 
importance, as G. chiroleuca thus serves as an intermediate step between G. nudiceps 
and Myrmelastes immaculatus and the allied forms which we now place next the 
genus Gymnocichla rather than in Thamnophilus, where they have latterly rested. 
Leyland obtained his specimen at Omoa, where he says only two or three birds came 
under his notice. They frequent thickets, and make a noise like the breaking of small 
twigs. 
Our single specimen was sent us from Tucurriqui, on the Atlantic side of the 
Cordillera of Costa Rica, by our collector Arcé, but without any note concerning it. 
The authorities of the Derby Museum at Liverpool have kindly lent us Leyland’s 
specimen, so that its specific identity with the Costa Rica type is assured. 
We are indebted to Mr. Ridgway for an inspection of a female and a young male of 
this bird. ‘The former is darker on the upper surface than the female of G. nudiceps, 
and has the edges of the wing-coverts more clearly defined. 
MYRMELASTES. 
Myrmelastes, Sclater, P. Z. 8. 1858, p. 274. 
Thamnophilus, Scl, Cat. Birds Brit. Mus. xv. p. 180 (partim). 
The type of this genus is M. plumdeus, with which Thamnophilus immaculatus auct., 
