PEOCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 461 



somewhat lengtheued, the terminal joint especially so. Tail double 

 rounded, the two outermost feathers being- much shorter than the others. 



Eemarks. — This genus embraces only one known species, the range 

 of which is very restricted, being found only in the high table-land of 

 southern Mexico. 



The bird forming the type of the present genus has not been removed 

 from the genus Turdus by any author except Mr. Seebohm. The jjlace 

 given to it by him within the genus GeocicJila, "subgeneric group ^Hes- 

 2)erocic7da',^" is, however, by no means an improvement. GeocicJila and 

 the nearest allied forms are exclusively Old World and Australian birds, 

 which have no true relatives within the Neogean part of the world, the 

 Eesperocidila nwvia being as badly placed among the Ground-Thrushes 

 as the bird here under consideration. The main reason of Mr. See- 

 bohm for placing the E. pinicola among these birds seems to have been 

 the pattern of its wing, although he candidly admits that the pattern 

 of the axillaries is not typical. Any one who will take the trouble of 

 comparing the bird here under consideration with a young Sialla, will 

 soon convince himself that the two genera should not be removed far 

 from each other, even if he embraces the doctrine that the coloration is 

 the only character of importance in regard to relationship. A close 

 comparison of the structural features of both genera corroborates this 

 view. The long and pointed wings, the short tail, and the exceedingly 

 short tarsi, make the Ridcjwayia widely distant from the Turdem and 

 Blerulecc, closely resembling in these respects the Sialia. Besides, it 

 will be remarked, that the geographical distribution of the two genera 

 agrees very well, thus making the Sialiecv a nicely circumscribed group 

 in this respect also. 



From Sialia the Ridgwayia is easily distinguished by the more length- 

 ened bill, the short gonys, and the double-rounded tail. Indeed it is 

 one of the best defined genera of the whole family. 



Sialia Swains. 



= . \^7.— Sialia Swaius. ZooL Journ. Ill (p. 173). (Type Motacilla sialis L.) 



{nee Selby, 1831). 

 = . 1839.— ^(aHs Lafresn. Eev. Zool. 1839, p. 162. CSame type) {nee Latr > 



1803). 



Smaller size; predominant color blue and chestnut, in the adults un- 

 spotted. Wings very long and pointed, with long primaries and short 

 secondaries; first primary normally placed, with tendency, however, to 

 the same position as in Ridgicayia, very short, not one-fourth the second. 

 Bill short, stout, compressed at the tip; commissure with a distinct 

 notch, and more or less curved; gonys of ordinary length, so that the 

 chin-angle is not produced before the line of the nostrils. Nasal fosste 

 filled with bristly feathers, only the openings of the nostrils being ex- 

 posed; bristles along gape more or less develox)ed. Tarsi stout and 



