No. 533] SHORTER ARTICLES AND DISCUSSION 315 



Three classes of birds were distinguished — adult males, young 

 males, and young and adult females. 



We draw the following conclusions from the comparison of the 

 means in Tables I-III with their probable errors. 3 



Length of femur. 



Tibio-hirsus 



Width of skull.... 



±.1420 26.2708=.1%6 .8023=.2424 



±.0709 31.6708±.0824 — .0565±.1095 



.7279±.0032 I + .0101 .mi.ss 



.7061 =.0027 + .0107±.0037 



