MYIAECHTJS. 93 



Truando river (C, /, Wood ^). — South Ameeioa 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 M. panamends in his list of 

 Costa Rica birds on the authority of " Enrique Arce," but we cannot find any record of 

 specimens having been sent us from Costa Rica by that collector. 



b. Minores (M. lawrencii &c.). 

 7, Myiarchus yucatanensis. 



Myiarchus yucatanensis, Lawr. Pr. Ac. Phil. 1871, p. 335 ' ; Eidgw. Pr. Biol. Soc. Wash. ii. p. 92 * ; 



Man. N. Am. B. p. 334'; Scl. Cat. Birds Brit. Mus. xiv. p. 260*. 

 Myiarchus mexicanus, Lawr. Ann. Lye. N. Y. ix. p. 202 °. 



Supra obscure olivaceus, capite paulo saturatiore ; supraoaudalibus rufescente tinctis ; alis nigrioantibus, 

 tectrieibus pallide fusco limbatis, secundariis internis albido margiuatis, remigibus intus et extus stricte 

 medialiter rufo limbatis ; cauda nigricante, reotrice extima utrinque anguste, reliquis (prseter duas medias) 

 in pogonio interno late rufo marginatis : subtus usque ad pectus griseus ; abdomine et subalaribus paUide' 

 sulphureis : rostro et pedibus nigris. Long, tota 7'0, alae 3'3, caudee 3"3, tarsi 0'85, rostri a rictu 0-85. 

 (Descr. maris ex Tabi, Yucatan. Mus. nostr.) 



Eab. Mexico, Merida in Yucatan (Schotf,^), Tabi (F. JD. G.), Peto, Cozumel I. 

 {G. F. Gaumer^). 



An obscure species, the position of which is not very clear. Mr. Ridgway sepiarates 

 it from M. lawrencii 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 M. lawrencii, from the 

 district named, has a more elongated wider bill and is of rather larger dimensions. - 

 Compared with M. lawrencii from more southern localities, including Yucatan itself, 

 the amount of red in the tail of M. 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. 



