Obs.—A very strongly differentiated form, but unquestionably grading into var. lawrencei on the one hand, and var. nigriceps on the other.
[77] Myiarchus tristis, var. nigriceps, Sclater. Myiarchus nigriceps, Scl. P. Z. S. 1860, 68, 295.—Coues, P. A. N. S. July, 1872, 75.
Obs.—The last three races appear to be all reducible to one species, as, taking the large series of specimens before us (over 30 skins), we find it impossible to draw the line between them. Specimens from Southern Mexico are referrible, with equal propriety, to lawrencei or to nigricapillus, while skins from Panama of nigriceps are less typical than those from Ecuador. This case of gradually increasing melanistic tendency as we proceed southward affords an exact parallel to that of Vireosylvia gilvus and V. josephæ, Sayornis nigricans and S. aquaticus, and many other cases.
[78] Myiarchus mexicanus, var. pertinax, Baird, Pr. Phil. Acad. 1859, 303.
[79] Sayornis nigricans, var. aquaticus. Sayornis aquaticus, Sclater & Salvin, Ibis, 1859, p. 119 (Guatemala).
[80] Sayornis nigricans, var. cineracens. Sayornis cineracea, Lafr. Rev. Zoöl. 1848, p. 8.—Scl. Catal. Am. Birds, 1862, 200. The above races are clearly shown to be merely modifications, with latitude, of one type, by the series of specimens before us. Thus, specimens of S. nigricans from Orizaba show more or less dusky on the lower tail-coverts, while in more northern specimens (i. e. typical var. nigricans) there is not a trace of it. Typical specimens of aquaticus, from Guatemala, show merely a more advanced melanism, the lighter markings on the wings becoming greatly restricted; there is still, however, a decided presence of white on the lower tail-coverts. Specimens from Costa Rica (typical aquaticus) exhibit the maximum degree of melanism, the white beneath being confined to a central spot on the abdomen. In cineraceus (from New Granada) the white beneath is similarly restricted, but on the wings is very conspicuous, showing a reversion back to the character of nigricans, though surpassing the latter in the amount of white on the coverts and secondaries.
The S. latirostris (Aulanax l. Cab. & Hein. Mus. Hein. ii, p. 68; Sayornis l. Scl. Cat. Am. B. 1862, 200), from Ecuador, we have not seen. It is probably also referrible to the same type.
[81] Contopus lugubris, Lawr. Ann. N. Y. Lyc. VIII, 1865, 134 (Costa Rica, Baranca).
[82] Contopus brachytarsus, Sclater, Cat. Am. B. 1862, 231. (Empidonax brachyt. Scl. Ibis, 1859, p. 441.) A strongly marked race, but distinguishable from schotti only by just appreciable differences in color (being paler beneath), and shorter wing and bill, the latter broader at the tip.
[83] Contopus (brachytarsus var. ?), var. schotti, Lawr. Ann. N. Y. Lyc. IX, 1869, 202 (Yucatan). Very nearly related to C. richardsoni, but easily distinguished by the very different proportions.