34 



BULLETIN 3(\, UNITiOD STATES NATIONAL MUSEUM. 



The four skulls of known sex iu the iiatioual coUectiou have the fol- 

 lowing absolute proportions : 



Measurements of four skulls of T. tursio. 



Measurements. 



Total length 



Length of beak 



Breadth of l)eak at notches 



I5rea(ltli of beak at middle 



IJreadth of intei maxilla) at middle 



Depth of beak at middle 



Length of tooth-lino 



Breadth across orbital processes of 



frontal 



Length of mandible 



Depth at coronoid 



Teeth 



Age 



Sex 



Condition. 



From these measurements we select the following for comi)arison 



Measurements. 



20901, ,/ a, 

 Fire Island, 

 N.Y. (young). 



Total length 



Length of beak 



Breadth of beak at maxillary notches 

 Breadth of beak at middle 



Cm. 



4.^.3 



22.4 



11.2 



7.0 



16504, cf h, 



Cherrystone 



Point, Va. 



(young). 



Cm. 



43.9 



24.1 



10.1 



6.9 



20902, $c, 

 Turkey Gut, 

 N.Y. (young), 



22304, $(Z, 

 Hattera.s, 

 N. C. (old). 



Cm. 

 44.0 

 21.4 

 10.3 

 0.4 



Cm. 

 52.9 



28.9 

 12.6 

 8 



A comparison of the length of the beak, relative to the total length, 

 and of the width of the beak at its base and at its middle relative to 

 its total length, gives the following results: 



The same diversity appears here as in the previous case. The old 

 female, which would be supposed to have the sexual characters strongly 

 marked, has a relatively shorter and wider beak at the base than one of 

 the young males, but a longer and narrower beak than the other. 



Coming uow to the series of twenty-one skulls, before mentioned, we 

 find the same variation. In some the beak is long and narrow, and vice 



