1891.] NEW YORK ACADEMY OF SCIENCES. 31 



nected mechanically, in an interesting manner, with the extremity 

 of the upper mandible — along the cavity of this mandible. 



The fact that immediately after the death of the bird, when the 

 bill is in its flexible condition, this opening of the bill, at its ex- 

 tremity, may be accomplished by any one who knows how to pro- 

 duce the proper action of the muscles, was discovered by Mr. C. C. 

 Trowbridge about two years ago, v/hile examining specimens of the 

 Hadsoniau godwit that he had shot. An examination of the 

 Avoodcock by him showed similar action. 



The solution of the object of the flexibility of the upper mandi- 

 ble at its extremity, connected with the fact that the opening of the 

 bill at the end (as in sketch No. 2) is under the control of the bird, 

 is doubtless as follows : 



When the bill is forced into soft around it must be closed to its 

 very extremity ; it then acts like an awl. To open the bill and seize 

 an object reached, if both maiuliljles were hard and inflexible through- 

 out their whole length it would be necessary for the bird to enlarge 

 the hole around its bill along its whole extent ; an operation requiring 

 much force, and possibly the opening and closing would be in such 

 case impracticable. But the opening at the extremity to the slight 

 extent necessary to take in its food is comparatively a simple mat- 

 ter. Moreover, when the food is seized and the bill withdrawn 

 through the small hole made by the bill the effect during the whole 

 of thewithdrawal of the bill is to cause the food to be clasped more 

 firmly and securely. The operation of withdrawing the food would 

 otherwise be very difficult, and possibly impracticable. 



Professor Trowbridge also presented the results of some further 

 observations made by Mr. C. C. Trowbridge, on the locking or 

 overlapping of the primary wing feathers by certain birds during 

 flight. 



Attention was called to the fact that about four years ago (Oct. 

 It, 1887) he had read a paper before the Academy descril)ing this 

 locking of the primaries of certain hawks, discovered by Mr. C. C. 

 Trowbridge, and stated that, as the number of specimens then ex- 

 amined was small, and although the fact of this habitual locking or 

 overlapping, especially during soaring flight, seemed completely 

 estal)lished for certain hawks ; yet from time to time observations 

 had been continued; a most remarkable opportunity for such ob- 

 servations having occurred this autumn during the month of 

 September. 



Large flights of hawks migrating southerly took place near New 

 Haven on the 8th, 9th, and Uth of September. On those days the 

 wind was northerly and high, and advantage was taken, for the 

 purpose of procuring specimens, of a high hill around which ha^yks 

 and eagles were circling. Large numbers passed within shooting- 

 distance, generally soaring, but frequently soaring and flapping 

 alternately. 



On SeiDtember 8th nine hawks were shot, on September 9th 

 three, on September 14th fourteen, in all twenty-six, embracing 



