RiDGWAV on Birds observed in Knox Co.^ Indiana. 1 5 



wing, would seem to be particularly liable to injury, sufficient, 

 we should think, to offset the amount it may protect the compact 

 carpals below. The extra area covered by the wing on account 

 of the ossicle is easily measured. It is simj^ly the area of a tri- 

 angle, which has for its base the difference in altitude between the 

 process of the metacarpus and the sesamoid ossicle, 3 millime- 

 ters say, and for its altitude the distance between the carjDus and 

 the origin of the extensor petagii longus, say 3.c; decimetres. 

 Absolute measurements cannot be given since no Hawks are to be 

 got in Boston at present. So the entire increase of area would be 

 3-75 square centimetres, and this increase is at the base of the wing, 

 where it would least increase the resistance of the wing. This dif- 

 ference becomes quite small in the ratio 3 ^ where a, 



V weight 



the area of one wing, represents hundreds of square centimeters. 

 Yet the ratio is that of the supporting power of the wing to the 

 weight of the body, other things being equal. In the above cal- 

 culation it is assumed that Dr. Shufeldt meant millimeters not 

 centimeters,* when giving the dimensions of the "os prominens." 

 To sum up, the bone serves : (i ) To keep the friction of the exten- 

 sor petagii longus muscle off the carpus. (3) To increase the 

 power of that muscle to abduct the thumb. (3) To slightly increase 

 the supporting power of the wing. (4) To protect the carpus ( }) . 

 Here it may not be improper to state that during the winter 

 of 1880-S1, the writer s/iozued a specimen of the carpus oi Accip- 

 iter fnscHS^ and explained his views as here stated of the function 

 of the " OS prominens," at a meeting of the Nuttall Ornithological 

 Club. 



NOTES ON SOME OF THE BIRDS OBSERVED NEAR 

 WHEATLAND, KNOX CO., INDIANA, IN THE 

 SPRING OF iSSi. 



BY ROBERT RIDGWAY. 



Monteur's Pond, situated about ten miles east of Vincennes 

 and two miles west of the village of Wheatland, on the O. & M. 

 R. R., is of considerable extent, being about nine miles long by 



* [See Erratum on p. 64 of this issue. — Edd.] 



