PHYLLOPNEUSTE. AVOODWRExN. 363 



The separation of the Wood wrens from the preceding genera 

 is rather arbitrary, as they diiFer merely in being more deli- 

 cate, with more attenuated bill and feet. They however bear 

 so strong a mutual resemblance that it is difficult to distin- 

 guish them specially, although the proportional length of their 

 outer primary quills affords a character sufficiently distinctive. 

 This circumstance, with other cases of a like nature, ought to 

 admonish those who place faith in the form of the tip of the 

 wing as affijrding a generic character. 



Fig. 173. Yellow Woodwren. 



Fig. 174. Willow Woodwren. 



Fig. 175. Chiff-chaff. 



