Ridgway 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 simply 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 carpus and 
the origin of the extensor petagii longus, say 2.5 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- 
\/ 2 a 
ference becomes quite small in the ratio 3 - 
where a , 
\/ 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 serv es : (1) To keep the friction of the exten- 
sor petagii longus muscle off the carpus. (2) 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 1880-81, the writer showed a specimen of the carpus of Ac.cift- 
iter fuscus , 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 1881. 
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. — E dd.] 
