36 



BULLETIN 31), UNITED STATES NATIONAL MUSEUM. 



the skull. The proportional leugtli of the beak in tlic diftereut sped 

 meus, arranged in an ascending scale, is as follows : • 



It appears tbat, excepting in tbe skull witb relatively longest beak, 

 tbe proportion of tbe lengtli of tbe beak rises by gradations of four- 

 tentbs of 1 per cent, and less. 



Tbe proportion of tbe widtb of tbe beak at its base to its lengtb is as 

 follows : 



40. per cent. 



40.1 



40.1 



40.4 



40. C 



40. 



47.1 



47.4 per cent. 



47.8 



49.0 



49.2 



49.2 



50.9 



51.2 



Tbe gradations bere are 1.7 per cent., 1.1 per cent., and less. 

 Tbe proportions of tbe widtb of tbe beak at its middle compared witb 

 its lengtb rise by gradations of 1 per cent, and less, as follows; 



In all tbrec cases tbe greatest variation is at tbe extremes of tbe 

 series. 



Wbat do tbeso proportions sbow I Apparently tbat tlio relative 

 lengtb and widtb of tbe beak give no indication of tbe sex. Unless 

 tbese twenty-one specimens are all of tbe same sex, wbicb is very im- 

 probable, for tbe reasons stated, tbe gradation of proportions is sucb 

 tbat it would be impossible to divide tbe females from tbe males. 



Tbe skulls of greatest absolute lengtb bave not relatively longest 

 beaks. Tbe beaks wbicb are relatively longest, as compared witb tbe 

 absolute total lengtb of tbe skull, are, generally speaking, narrowest at 

 tbe base and middle in i^roportion to tbeir absolute lengtli, 



Tbe lengtb of tbe mandible as compared witb tbe lengtb of tbe skull, 

 minus tbe beak, is greater iu all of Dr. Fiscber's males tban in bis fe- 

 males. In botb of my young males (20901 and 10501), on tbe contrary, 

 it is sborter tban in tbe young female, 20902 ; and in one of tbe former 

 (20901) it is sborter tban in tbe old female, 22301. 



