OSTEOLOGY OF BIRDS 8 I 



centimeters taken from apex to tip of that process which is the 

 superior one when the foot is in the position of standing. 



The first phalanx of the inside toe is a short, and, at first sight, 

 very irregularly shaped bone. 



Above, it is convex from side to side and presents a small tubercle 

 on its inner aspect. Longitudinally the superior surface is limited, 

 the two articular facets nearly meeting. Its lower surface is power- 

 fully grooved for the passage of the flexor tendons, and its prox- 

 imal end is fashioned to articulate with the tarsometatarsial trochlea. 



The articular surface intended for the proximal end of the 

 phalanx beyond, occupies a space both above and below the end of 

 the bone. It is surrounded by a raised marginal rim, which allows 

 the succeeding phalanx scarcely any motion in the vertical plane, 

 and these latter joints of the digits have it in no other. 



The second phalanx of the inside digit much resembles the first 

 digit of hallux ; it is, however, a smaller bone ; the same may be said 

 of its claw, though we note that the curvature is less in the one 

 under consideration. 



The irregular first phalanx measures seven millimeters in longi- 

 tudinal axis between parallel lines which touch its most distal and 

 proximal points. Second phalanx measures 1.7 centimeters on the 

 chord of the claw measured as in the first instance 1.9 centimeters. 



The four phalanges of the middle toe in Circus all more or less 

 resemble the typical style of the joint, i. e. like first phalanx of 

 hallux. From proximal to distal one, the first three measured 

 1.6, .8, and 1.5 centimeters respectively; the chord of the claw be- 

 ing 1.6 centimeters. 



Measured in the same manner the joints of the outside toe give 

 .8, .5, and .45 centimeters, and the chord of this claw 1.3 centimeters. 



Ossification occasionally extends, in Circus, to some of the ten- 

 dons of the lower extremities, in subjects several years old. 



The usual parts of the sense capsules also ossify, as the sclerotals 

 of the eye, and the columella auris of the organ of hearing. 



I complete this account with a recapitulation of the principal 

 characters of the skeleton in this harrier. 



Osteological characters of Circus hudsonius 



1 The nasal septum in the dried skull is not complete, there being 

 a deficiency at its superoposterior angle. 



2 The osseous nares are of an elliptical outline on either side. 

 the major axis being in the same straight line with the imaginary 



