VIREONIDiE. , 325 



restricted, is so slight, while those agreeing in one or other feature 

 differ so much in the remaining points of structure, that it is almost 

 impossible to group them satisfactorily, and we can only make a few- 

 arbitrary sections of no great sharpness of definition, to aid in 

 identifying the species — one of them Vireo proper, with longer, 

 more pointed wings ; the other Vireonella (Baird), with the wings 

 shorter and more rounded.' 



The following synopsis is intended to show the characters of the 

 higher divisions of the group just referred to : — 



ViBEoSYLviA. Wings long and pointed, one-third or one-fourth longer than 

 the nearly even or slightly rounded tail. First quill very small (less than 

 one-third the second), sometimes apparently wanting. Second quill 

 longer than the seventh, much longer than the secondaries. Tarsi short 

 (scarcely exceeding .70 of an inch) ; toes rather long. 



Vireosylvia. Body slender and elongated. Bill slender, narrow, straight ; 

 the oulmen straight for its basal half, the commissure quite straight ; 

 light horn color, paler beneath. Feet weak. Type F. olivaceus. 

 Species V. olivacea, Jlavoviridis, campestris^ barbatulaj agilisj chivij 

 philadelphica, gilva, swainsoni, josephse. 



> Allusion has already been made, on page 160 of the present work, to the 

 possibility of detecting a rudimentary primary in nearly or quite all the 

 Oscines which seem to have but nine. While the apparent presence or 

 absence of this outer quill is sometimes useful in characterizing genera or even 

 families, in Vireosylvia it is only of specific importance — the diflFerence being 

 merely one of development and position of the quill. In V. flavifrons, in 

 which this outer primary is supposed to be wanting, its presence may easily 

 be appreciated. One of the peculiar characters of this species consists in a 

 narrow edging of white to all the primary quills, while the primary coverts 

 (the small feathers covering their bases, as distinguished from what are usu- 

 ally termed the wing coverts, which more properly belong to the forearm or 

 secondaries) are without them. If these coverts are carefully pushed aside, 

 two small feathers, considerably shorter than the others will be disclosed, one 

 overlying the other, which (the subjacent one) springs from the base of the 

 exposed portion of the long outermost primary, and lies immediately agains* 

 the outer edge. This small subjacent feather is stiff, falcate, g,nd edged with 

 white like the other quills, and can be brought partly round on the inner 

 edge of the large primary, when it will look like any spurious quill. The 

 overlying feather is soft, and without light edge. 



In the other Vireos with appreciable spurious or short outer primary, a 

 similar examination will reveal only one small feather at the outer side of the 

 base of the exterior large primary. In all the families of Passeres where the 

 existence of nine primaries is supposed to be characteristic, I have invariably 

 found, as far as my examinations have extended, that there were two of the 

 small feathers referred to, while in those of ten primaries but one could be 

 detected. 



