Vol i907 IV ] Bangs, Birds from Western Costa Rica. 289 



then to Dr. Robert Ridgway, Mr. E. W. Nelson and Mr. J. H. 

 Riley, who made many comparisons for me with material in Wash- 

 ington. 



A complete catalogue of Underwood's collection made in western 

 Costa Rica in the spring and summer of 190G, in which colors, 

 when definite names are given them, are according to Ridgway' s 

 'Nomenclature,' and all measurements are in millimetres, is as 

 follows : 



Akdeid.e. 



Butorides virescens maculata (Bodd.). Two males, one fully adult 

 tke other youngish, Pozo del Rio Grande, April. 



These skins agree with others from Panama, etc.. and in my opinion 

 are identical with the bird of the West Indies. 



Axatid.e. 



Querquedula discors {Linn.). Four adults, one male, three females, 

 Pozo del Rio Grande, April. 



Falconid.e. 



Micrastur interstes sp. nov. 



One young male Pozo del Rio Grande, Aug. 4. 



Type, from La Estrella, Cartago, Costa Rica, adult cj , No. 16414, coll. 

 of E. A. & O. Bangs, collected xMar. 28, 1903 by C. F. Underwood. 



Characters. Similar to Micrastur guerilla Cassin of Mexico, Guatemala, 

 Honduras etc. but slightly larger, the adult male with the underparts 

 darker — the dusky bars broader and the pale interspaces narrower and 

 grayer, less purely white, in color; the whole belly, thighs and under tail 

 coverts heavily barred with dusky, whereas in M. guerilla the middle of 

 the belly is white (unbarred or nearly so) and the thighs and under tail 

 coverts are narrowly barred, the dusky bars far apart; white bands on 

 tail wider, more conspicuous and more complete. The adult female 

 differs from that of M. guerilla as does the male, but the differences are 

 not so marked as in the other sex. Young birds of the new form are much 

 more heavily barred below than young of M. gu n rilla, and the barring 

 includes the belly, which is plain in M. guerilla, and the ground color is 

 darker and more ochraceous. 



