MYIARCHUS. 93 
Truando river (C. J. Wood 3)—Souta America generally southward to the Argen- 
tine Republic 4. 
This bird is subject to very considerable variation throughout its wide range, some 
examples being much more olivaceous and paler on the back than others which are 
darker brown with darker heads. In most South-American localities we find darker 
and lighter birds together with intermediate forms in nearly equal proportions, but in 
the State of Panama we have as yet only met with the paler olivaceous form. This 
was described by Mr. Lawrence as Myiarchus panamensis ; but we are not convinced of 
its specific distinctness, for it is by no means confined to the State of Panama, and in 
the south becomes inextricably involved with darker forms. 
Mr. Lawrence’ (followed by von Frantzius%) includes MZ. panamensis in his list of 
Costa Rica birds on the authority of “ Enrique Arcé,” but we cannot find any record of 
specimens having been sent us from Costa Rica by that collector. 
b. Minores (M. LawRENcI &c.). 
7. Myiarchus yucatanensis. 
Myiarchus yucatanensis, Lawr. Pr. Ac. Phil. 1871, p. 235+; Ridgw. Pr. Biol. Soc. Wash. ii. p. 927; 
Man. N. Am. B. p. 334°; Scl. Cat. Birds Brit. Mus. xiv. p. 260°. 
Myiarchus mexicanus, Lawr. Aun. Lyc. N. Y. ix. p. 202°. 
Supra obscure olivaceus, capite paulo saturatiore; supracaudalibus rufescente tinctis; alis nigricantibus, 
tectricibus pallide fusco limbatis, secundariis internis albido marginatis, remigibus intus et extus stricte 
medialiter rufo limbatis ; cauda nigricante, rectrice extima utrinque anguste, reliquis (preter duas medias) 
in pogonio interno late rufo marginatis: subtus usque ad pectus griseus ; abdomine et subalaribus pallide 
sulphureis: rostro et pedibus nigris. Long. tota 7:0, ale 3:3, caude 3°3, tarsi 0°85, rostri a rictu 0°85. 
(Descr. maris ex Tabi, Yucatan. Mus. nostr.) 
Hab. Mexico, Merida in Yucatan (Schott*), Tabi (Ff. D. G.), Peto, Cozumel I. 
(G. £. Gaumer *). 
An obscure species, the position of which is not very clear. Mr. Ridgway separates 
it from WM. lawrenciit by the shape of the bill, which is less flattened and deeper through 
the middle. This is not altogether a satisfactory character, and we see very little 
difference between these Yucatan birds and the form of M. lawrencii found in Eastern 
Mexico from Vera Cruz northwards. Both have a considerable margin of red on the 
inner web of the tail-feathers (except the outermost pair), but J. lawrencii, from the 
district named, has a more elongated wider bill and is of rather larger dimensions. 
Compared with MZ. lawrencii from more southern localities, including Yucatan itself, 
the amount of red in the tail of IZ. yucatanensis becomes a more conspicuous character, 
and the difference between the two is more obvious. 
We have now a fair series of this species, which shows that its range is restricted to 
the promontory of Yucatan and the adjoining island of Cozumel. 
